Yet another Grounding Question-Separate 'Earth'

Many thanks to all of you, and to Nsgarch, for the timely responses. Work will be done by the book, according to Code and to Hoyle. The balanced power idea is also intriguing. I will let you know how it goes and will scream if I have questions in the midst of it. Thanks again, everybody.

I hadn't been down to the basement to look at his work- here's what we have right now: a Square D subpanel is feeding off the main panel, fed by a metal insulated cable that appears to be close to an inch in diameter. No further work has been done (yet)- he will return later this week. I suspect that when he said he wired this panel in, 'upstream' of the existing box, he really meant upstream of all the existing breakers, perhaps, save for the main power breaker on the incoming service.
The ground wire out of the main box is a massive thing, looks like its multistrand, also probably an inch thick, wrapped in a light grey, rubber-type insulator.

I'll make sure I discuss these postings with him. He has done good work for us in the past, and is pretty meticulous. Perhaps he didn't mean that the ground to the subpanel would be totally isolated, and that the panel wouldn't also grounded to the main house system, but I sure heard it that way.
As to problems I'm trying to solve, well...

The room in which the hi-fi exists is already overcrowded with other equipment for the video system. My preference would be to install the audio only system in another room, but at least for now, that's not possible.
I'm pretty fanatical about the noise level in the system, and have tried myriad ways so far to reduce the noise level at idle. (As mentioned in another post, an industry guy who I respect for his technical knowledge heard the system a couple weeks ago, and scoffed at my complaint that the system was noisy).
In any event, the video system is powered by its own dedicated 240v stepdown transformer. That in turn handles the power for the various 'audio for video' amps and also supplies the juice to a big Richard Grey box which powers the projector, line doubler, and small signal video stuff.

I want the audio system totally isolated from that, and I'm moving the audio equipment (other than the speakers) to another area of the room --partly to get it away from my ears, and partly because the compressor for the Air Line arm can then be stashed in its own little room, isolated from the listening environment.

In doing this, I just want to make sure I have the best possible AC feeding the system. The current demands made by the system are modest. While I am currently using Shunyata Hydras, I'd also like to hook up without them, and see what the difference is. At present, the other outlets in the room are not 'dedicated' and are part of the standard electrical system that was installed in the room about 5-6 years ago, when the upper floors of the house were substantially renovated.

ps- house has 200 amp service, all upgraded about 5-6 years ago when the house was massively upgraded by the prior owner.

OK, not to add to the confusion, but to answer the questions:

We have 200 amp service, goes into a main panel with one big breaker, littered with all kinds of smaller 15 and 20 amp breakers (box is quite full), and an existing subpanel that appears to be set up for some of the kitchen appliances.
The new subpanel is a 100 amp box, set up right now with 3 Square D 20 amp breakers. I'll check to see if he installed a 60 amp breaker in the main panel to support this new subpanel.

It was my intention to have him set up a number of 20 amp dedicated lines from this new subpanel, strictly for the audio-only system, and rather than have him ground the receptacles at each wall box, to run separate ground wires back to the subpanel for each- not daisy chaining the receptacles to each other. I have ordinarily used Hubbell Hospital Grade receptacles- only because of habit, and because i know Bill Hubbell, and figure his trust fund needs the money (He is a serious car junkie).

The run from the panels up to the room is easily 75-100 ft., depending on routing.
The only reason I hadn't considered another transformer for this system is that the one currently used in the video system is located in the room, inside one of the Mid-Atlantic racks, and I can hear it hum at idle, when all the video equipment is shut off. (When the video system is on, the fan noise masks that). I suppose one could set up an isolation transformer down in the basement, near the panels, but would that defeat the purpose if the outputs of the transformer then have to make that long run? Apologies in advance for my ignorance.

OK, went back down and checked- no new 60 amp breaker that I can see in the main panel, to support the new subpanel. Is it possible that the subpanel is wired as if an 'extension' of the main panel, and that he fed it, and its array of 20amp breakers from the main panel, but before any of the other breakers (other than say, the monster one at the top of the panel?) This would explain his statement about setting it up 'upstream' of the existing breakers (sic).
Obviously, I will ask him when I ring him tomorrow. He won't be back to my house until mid-week, so I'm sure I can get the skinny from him, and let you know as we proceed. Thanks to all so far, and particularly to JEA 48 for all your follow up on this. Regards, Bill Hart

OK, here's the scoop: Richie, the electrician, completed the wiring of the new outlets to the room, as follows (BTW, I printed out this thread for him to read, and apart from a few questions about his competence, he explained to me why what he did met Code and was otherwise kosher): the 3 20 amp circuits are wired to the subpanel using #10 wire and each has a separate ground back to the subpanel. The subpanel ties into the main board at the 200amp breaker, but before any of the other breakers in the main panel. It shares the same ground as the main panel, but has an additional ground to earth in proximity to the house grounding rod. The subpanel is protected by its own 60 amp breaker, which then feeds the three 20 amp circuits. The subpanel is mounted adjacent to the main panel.
Since local supply houses did not have the Hubbell receptacles on hand, I bought a bunch of Porter's tweaked Hubbell receptacles.
Now, for the punchline. Perhaps a little less noise than when hooked up to the regular house outlets, but still suffering some grounding noise issues. Prior to installation of this new electrical subsystem, my best result was obtained by deriving all system power from the same set of outlets.(Remember, I don't draw a huge amount of current with this system).
Obviously, once I 'cheat' everything but the preamp, the grounding noise goes away, but I am still reluctant for safety reasons to lift the grounds on any of the equipment.

I have achieved quietude right now with the following arrangement- the Duo bass amps remain grounded through the 3 pin cord (Shunyata) plugged into a Hydra 2 which goes (with 3 pins) into one of the three new dedicated lines. (Each speaker has its own Hydra 2/Shunyata cord array, fully grounded, plugged into its own wall outlet right behind the speaker- both 'speaker ac' receptacles are on the same dedicated line- call that dedicated line "3").

The Lamm L2 line stage is plugged directly into the wall on dedicated circuit 2, no cheater. Ditto, the Steelhead phono preamp. Floating the ground of the STeelhead or not makes no discernible difference, so I have not cheated it.
The Audiopaxes are plugged into a Hydra 4/Anaconda which goes into dedicated circuit #1. Here, to get rid of the hum, I have to lift the ground on the amp cords going into the Hydra 4. (The Hydra 4 is using all 3 pins into the wall at dedicated circuit # 1 but viewing the Hydra as simply a wall receptacle extension, the amps really aren't
'grounded.')
I also tried plugging the Hydra 4/Audiopaxes (no cheater on the amp cords) into dedicated circuit #2, which powers the Lamm line stage, and no improvement.
I have hooked up the Granite Audio Ground Zero product, and have separate ground lines from the Duo amps, the Audiopaxes(cheated, as above), and the Steelhead all converging at the Ground Zero device. With some experimentation, this yielded a relatively quiet, hum free system, but if I ground the Ground Zero to a wall socket, using the supplied 'dummy' 3 pin plug, the hum is back.
For safety reasons, I'd still prefer to be able to avoid any cheaters. To sum up, right now, the only cheated plugs are on the Audiopax amps. (I assume that unplugging the Hydra 4 from the wall when I am not using the system makes no difference for safety purposes, since the amps are still connected to the rest of the system via the interconnect and speaker cables).
So, if you've hung in with me so far, it seems that there is almost no way around lifing the ground in this system somewhere to make it noise free. The grounding problem is an 'intercomponent' grounding difference, and not a bad ground from the wall. The grounding differential appears to be between the Audiopax amps and the amps in the subwoofers.
The only thing I didn't try was to also hook up the Duo subwoofer amps to the same dedicated circuit as the front end electronics- I could try that, which would mean the whole system is running on one 20 amp circuit- probably not a problem from a current draw perspective, but it would mean , if that worked, that I would have to have Richie rewire the outlets now on circuit 3 to tie into circuit 2 instead- I will test this temporarily before having him do that. It also means that having multiple dedicated lines for the same system is pointless, given the grounding differential between the circuits.(And, to the extent there is some subtle benefit to having more current on hand, despite the modest demands of my system, I am losing the benefit of that by forcing everything to feed off one 20 amp line).
With sincere apologies for the length of this post, I invite any thoughts or suggestions (:)!

oops> One last thought. Preamp fully grounded. Ground lifted on Audiopaxes. But, both components have separate ground wires to the Ground Zero device. Does this mean that the amps are effectively grounded via the preamp? Is that true even though the various connections on the Ground Zero are 'buffered' from one another?( ie, the Ground zero allows separate ground connections that interact with each other thru multiple position 'impedence' switches).
And, note that the Ground Zero is not itself separately grounded since if I plug its dummy ac plug into a wall outlet, the hum comes back.
Just to add to the confusion.:)