My m80tis arrived today, what an absolutely amazing sound. I was lucky enough to try them at a friend's place, and am really pleased that they sound just as great at my house.

Currently, they are part of a 2.0 setup (Denon 685 amp). I will eventually upgrade this all to 5.1, but in the meantime, I'm thinking of filling up the back of the room on the B channel.

Would it be reasonable to use the surrounds (QS8 most likely) in a 4.0 setup? I don't imagine there is anything 5.1 specific about how they work; and as this is a temporary setup, I'm willing to trade off some performance.

If you mean simply duplicating the two stereo channels with two speakers in back, sometimes referred to as all-channel stereo, that certainly can be done and some people like the surround effect although it isn't really a natural one. Identical speakers in back would be better, of course, but as a temporary measure to hear something different, why not?

giro, i use two 8's as rears with my 60's, and think they sound great. my rear 8's are for the surrounds too. had to compromise with the bride.
dan