The speakers are set up in roughly a 3m equilateral triangle with the listening position. The toe-in is such that I can just see the inside flank of each speaker.
The one passive one that I did try was probably the best sounding pc that I have tried but it didn't do much to clean up the worst of the AC noise (dimmer switch noise, for instance).
I suggest installing dedicated lines for your sound system. I have 3 dimmers and my system is dead quiet. It's an all tube system but I have 2 20amp dedicated lines.
I have now tried the Audience aR6-TS and the Bybee Stealth Power Purifier in my system. In both cases I much preferred my stereo plugged straight into the wall. At this point Ive pretty much given up on audiophile power conditioning.
I was in similar boat so I demoed a passive Weizhi PRS-6 and never looked back. Now I have 2, one for mono amps and the other for rest of system.
I heard good things on HB Cable Design Power Distributors too.