Power Conditioners: Myth, Magic, or Necessary

My experiments
I live in a rural area, about 50 houses around my home. About 300 yards from my house is the HQ of local cable, telephone, and the internet provider’s office.
My home theater system consists of AVA FET valve hybrid amplifier, an omega Star pre amplifier, 3 channel Power amplifier, Onkyo DVD player, Omega star DAC, EFE speakers, Monster 1000 HTS power surge protector and conditioner.
The picture quality and audio is lot better in the late night. .
I assumed the sub optimal audio and video in the day time is from power polluted power and cable TV signal.

I am interested in getting the audio quality during day time and evening.
I followed some of the suggestions
Cleaned the connectors, RCA plugs, metal prongs for the power plugs, speaker terminals etc with De Ox. Separated and spaced the cables, ICs with dowels, and foam spacers... Elevated all the cables from the carpet using Jeweler stands made up of ceramic about 4 inches from the ground.( available at Wal-mart during Christmas season.3 $).I connected
Digital and audio components- to different outlets. I purchased a separate digital power filter with 4outlets for 120 dollars from virtual mode to which I
Connected Cable TV box, TV, DVP player and DAC)
The audio portion improved with less background noise. But video image remained the same.
The new Cables, Composite for the video from better cables com did not help much, component cables from ZU megular improved the color saturation .Fine tuning with Avia video set up disc did not help much with graininess of the picture other wise did improve the color balance. I tried video coaxial cable noise filter and surge protection filter on the Monster 1000.It attenuated the sound.
I purchased a video noise filter from Virtual mode for 6 $.it improved some .Parts express also sells one for 9 dollars.

Using ferrite core on the cable company co ax cable made the picture dark. It did improve the picture a little when attached to the power cable TV digital box.

I checked the RF with a portable AM Radio tuned in between stations. The cable TV box and the DVD player produced more noise. I separated Digital and analog components on the rack and the Cable TV box went on the Top of rear projection TV away fro the analog components.
There is a definite improvement but not in the same league as the Picture at late night or the very impressive audio at mid night.
I purchased Blue circle 86 noise hound/pillows mark2 for 100 dollars each including shipping from a dealer at audiogon.
Connected them to the power outlets directly they do improve, no back ground noise, clearer, better definition, bass .more closer to the sound and video during the day and evening but not the same quality at 2 AM.
I do not want to change the power lines as I live in a rented house, but I will change the power plugs later.
I do not plan to spend S1699 for audiomagic magic stealth.
I am lookig for a cheaper solution.
Will continue later with my further experiments

I do know from experience that, as others above have attested, different components will benefit to differing degrees from AC power tweaks. Your amps simply may not need this treatment to sound good. Or, your system (or ears) could be failing to inform you of the differences, which can range from large down to subtle in nature. And then there are always the matters (as was also mentioned above) of *which* PC you're using, and how contaminated your AC is in the first place.

So I'll just bring up two things additional here. One being that, other than your AC quality straight out of the wall, there's also the issue of stray environmental RFI/EMI to be protected against, and the possibility exists that in your particular location and system, this may simply not be a big problem. The other thing is that in many instances, it can be source components that will reveal the most benefits from an upgrade PC, so before you sell the cords, you may want to try them out there instead just for grins.

I have found that filtered power, and especially balanced filtered power, can and does make a positive (though not life-changing) difference, particularly on my digital front-end, so you may still want to try a PLC out. But after all is said and done, I agree with Tim and the others - if you can't hear an improvement, then be all means get rid of 'em and just enjoy your music!

How to decide if your system needs conditioning is the big question. Some thoughts:
1) If you see an improvement late at night.
2) Turn your volume up with nothing being played. How far do you turn the volume before hearing "white noise"? In my case I hear nothing even inches away from my speakers until the 12:00 o'clock on the volume. Since I listen at 8-9:00 them EMI/ RF is probably not a problem.
3) Try a "noise sniffer" sold, I think, by Quiet Lines or Audio Prism. If this thing has no noise probably not in your system.

Vrsola, you can get a mini-stealth for $499 from one of A-gon's "approved dealers". I forgot which one. They normally retail for $599. It is a 2 outlet version of the Stealth and the mfg'r told me identical in every other way.

Cdchas the right test. I am able to turn the volume up 100% and hear nothing 3" from the speakers. Just for fun I tried plugging everything into a standard outlet with stock cords and at 50% volume I could hear a whooshing noise from my listening position.
As far as the scam of power cords and conditioners, I have come to believe there is a lot of products out there that do little to nothing. I have tried a great deal of power cords and conditioners, and it's the power cord business that I most suspect. I found very little of true improvement in the $50-$700 price range. Most of the more expensive cords I tried di indeed help.
I live in a very quite suburb and receive my power from a pole mounted transformer 50' from my house. I am the only user on that transformer, so if it's possible to get great power I've got it. Power cords, dedicated circuits, outlets and conditioners all help my system. As the system has improved and become more detailed, the need for clean power increases. Perhaps the people who hear nothing have larger issues to address first.

power conditioners
contd
Some basic things which I ignored.
(1)One day I saw the ground connection for my TV cable was broken.This was done by the lawn mowing service person.

(2)The Power cables, speaker cables,Interconnects which I separated them, and elevated from the carpet are on the floor,parallel to each other probably dislodged themselves as they are stiff or by my spouses cleaning efforts.

all the above 2 I corrected promptly

I also obtained a cheap quantum clear power module(about 40 dollars from an audiogon dealer) and connected it to the TV.
Instead of using 2 wall outlets, I used a third one near by.
Now the TV picture is also close to the picture at the late night.The audio also improved significantly,closer to but not exactly the same as late night listening.

The only thing I can say is- Start from basics, check them frequently( cables, ICs, ground etc)
separate digital components including to TV,DVD, CD, DAC and the Cable Box to another outlet and power cleaner.
The quantum power cleaner for 40 dollars is fine and it works.at least for me in TV.
regards