From the 7100's manual:
The high current power supply is driven by a custom-designed 1.2 KVA torrodial
transformer with two separate windings for each of the seven channels.
I think that means you won't have to worry about two channels sucking the juice from the other 5
Incidentally, I use my 7100 to power 5 speakers and a subwoofer, and there are never drops in sound levels or clarity. I have no center channel, and a single rear surround.
-Joe
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