OK, gotta be the voice of sanity here \:\)

The M60's will be fine in your room. I have M60's in a similarly sized room, connected to an Onkyo 705. I agree with going 5.1 instead of 7.1 if you don't have room behind your listening area.

BTW - I have 4 QS8's for my 7.1 setup and I really like it. However, I did have direct speakers for my rears in the past and I liked that as well.

Dave
Audyssey Setup Guide