jrmav -
I just picked up a pair of M1s from that same vendor for the same purpose. I haven't hoooked them up in a 7.1 configuration, as the new receiver is still pending. I did set them up as the mains w/ my existing receiver. For such a small speaker, the sound is pretty darn good. I almost picked up a second pair to go upstairs and replace my old dinosaur Yamahas. However, they couldn't quite fill that role, even w/ a sub. The quality and/or clarity was much better, but they couldn't hold their own in terms of filling such a large room. However, I have no fears concerning their performance as rear or side surrounds. They were quite a steal.
FYI...If it's the same guy that I dealt with, you should give him a call. He will hook you up w/ a better price. Also, if it's the same guy, you can find them on Ebay too.
Good Luck
