floorstanders on carpet over concrete

I think you could try slabs under the speakers but that doesn't usually remedy too much, more of a tweek then a tuning device. I think your problem could be room related and bass traps are an option, helmholtz resonator's(aka room lens) could work as well; different rooms, systems and listening preferences have different requirements. You also may want to try moving your speakers a little bit, spiking shouldn't make them unlistenable. Also if this problem happened only after the new dedicated outlets, you could have taken power from the 'dirty' side of the box- the side with the washing machine, refrigerator, etc... a simple fix may be to move the breakers to the other side of the box and possibly replace the grounding rod you are currently using. I would try plugging your gear into different outlets first, if the problem seems to go away it is not room related(entirely) but if it remains then you have a good place to start. If the new lines are the problem then you should track down the problem with them and it should be fairly simple to fix. What ever the case is this doesn't sound like it should be keeping you up during the nights, get things back to normal and enjoy the music.

You might try a set of Aurios Pros under the speaker spikes, four to a speaker. They will certainly isolate the speakers from the concrete floor, and clean up the bass. Not inexpensive, but what tweak is these days? Audionuts is one dealer which carries them.

After I purchased some power cables and began experimenting with them, I noticed that things which 'tightened up' the A/C power's waveform made the Bass 'thinner' sounding.
Do you use any powerline conditioners?
And if not, borrow one to try on your amp... it may help tighten up the Bass.
But I think your real problem is the room. A carpeted concrete floor is usually Bass neutral.