I just got my 950+7100 and connected it all. I have exactly the same problem, 7100 hums loudly. I had really good luck with 1050, that unit was silent when no signal was sent to. I tried Denon 3803 and it did not make any parasite noises either.
I ruled out Ground Loop by simply unplugging my speakers. I can easily locate the noise, it sounds like the old transformer. Somehow, I am not buying into the idea of bad power because neither Denon nor 1050 made any noises, and they were connected to the same AC outlet. I do not feel that I need to spend $400 on AC conditioner to get 7100 to work for me.
Is Outlaw exchanging 7100?