1. I am using QS8. I experimented with M22s and in the end, I got more satisfaction from QS8
2. Percentage of 7.1 is fairly small, but there are quite a few Dolby EX and some DTS:6 even from before BD. No idea if it is growing or not
3. The rear channels are used the same way as center channels and surrounds are used for stereo. Phased stereo is detected (between the two side channels) from the source and re-mixed to be played from a more acurately (spatially wise) positioned speaker.
ABOUT THE NOTICING: When I moved from 5.1 to 7.1, it was the least noticeable difference. BUT BUT BUT, a few months ago, I lost 2 channels on my A1400 and had to get down and recalibrate for a 5.1 system for a while. I really, really missed the immersion and was very happy when I got it back. Bottom line: I used to be very borderline on the 7.1, but now I would not go back.
