elikd: a very well thought out and reasoned post!!!

readster: it is highly unlikely that you would EVER use 300 watts in all 7 channels at the same time. My speakers are rated at 91 dB SPL for 1 watt. 300 watts would be about 25 dB more. I find anything over 87 dB to just be too loud. I would not be playing anything in my house at 116 DB SPL!! If you can get or borrow a sound meter, make a few measurements. I think that you would be surprised.

There is nothing wrong with having an amp that runs 300 for each of 7 channels. I may get one myself. But, I would be surprised if your 20 amp circuit is not sufficient for your listening pleasure.