My system is actually on 3 different circuits right now. Most everything is on one, but the left sub is on it's own, and the ButtKicker on another. No hum or ill effects at all.

It's just that if you get hum, that's one of the first things to check.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris