PB, I'll try and take a minute to look into the two balanced models you mentioned and post any pros/cons I might discover. If I forget, feel free to email me and remind me ;-)
As for your other quandries ;-) here's my approach:
1.) Put in those dedicated circuits - biggest bang for the buck in audio! Here are the finer points:
a.) Two separate 15A circuits near your sources; not for extra capacity but to keep analog and digital separate.
b.) One 20A near the amps/speakers in the center of the end wall OR (just as an alternative, but especially if you are running monoblock amps) two 15A circuits, one on ea side of the room.
c.) Believe it or not, Romex is better than twisted wires in a conduit because the latter creates inductance, and RFI is better taken care of at/by the equipment itself.
d.) If your receptacles will be more than 20' from your breaker panel, go up one wire size from code to make up for voltage drop over longer distances. I.E. 10AWG versus 12AWG.
e.) Make sure the breakers for all your ded. cts. are on the same side of the neutral buss in the breaker panel box to insure they are all in phase.
f.) Use Hubbell hospital grade receptacles (with the green dot) because they have clamping connectors for the wire, as opposed to screw terminals (NEVER use 'push-in' connectors!)
2.) Voltage fluctuations: Once you've installed your ded. cts. you need to check the wall voltage at different times of the day (and night/evening.) It should not vary more than 5% over all (117 - 123 VAC) If it's higher or lower by more than just a volt or two (115 - 125 VAC), more than just once in a great while, and just for a few seconds, then you'll need voltage regulation, especially if you have tube gear. There are many inexpensive ways to do this. The least expensive being a voltage regulator(s) (duh! ;-) of the proper capacity. But, if it's a serious problem (like it's just too high or too low too much of the time,) I would FIRST talk to your utility company - they might need to replace a pole transformer!
3.) Subs with digital, or ICE, or Class D amps, should go right into the dedicated circuits' wall outlets. They create more noise than they are affected by it, and you don't want them dumping digital hash and in-rush current surges into your carefully balanced or regenerated power, from which they won't benefit anyway. They CAN benefit from big 10AWG power cords however ;-)
4.) If lightening and/or huge power surges are a problem in your area, the ONLY intelligent practice is unplugging your entire system. Seriously! Lightening can jump right across open circuit breakers and still fry your system -- so unplugging is the ONLY way except for: big isolation transformers. They will electrically separate your stuff from the grid (lightening) smooth out power surges, and eliminate a lot of noise. If I still had a house of my own, I'd combine dedicated circuits with isolation transformers, and be done with it!
Neil
.