I have the M80, VP150, QS8 (SVS 16-46+ on the way).
This package sounds great! My room is 10.5 x 27 x 7.5 (just over 2100 cf) and have a 6 foot entertainment unit which only leaves me with 2 feet per side for my M80s. The space behind the M80s is different on both sides due to the duct work,etc (about 3' for the left and 1' for the right and 18 inches behind the 2' deep entertainment unit).

I think as long as you have space behind the speakers, it should be OK.

As for surrounds, I agree with Ian in putting 2 on the side walls and the third on the back wall (perhaps using a direct radiating speaker like the VP150)

GOOD LUCK

kevin