I know that most people suggest the QS8 as best for surround usage, but I was wondering if anyone had tried multiple sets of M2i's instead? Im considering using 2 sets as side speakers and another set on the back wall as rear surrounds (total of 6 speakers).

Any thoughts?

Why do you need two sets to the sides? I think one set should work. I have tried the M2i as surrounds and they work great!

The basement room I plan to put them in used to be a garage, its 17 by 26 (long and narrow). The ceiling is about 7' 8" and has a beam running crosswise that comes down another 10". Im concerned that if I put the speakers in front of the beam then the sound will be markedly different behind it (or vice versa).

I know in real theaters they use multiple sets of direct radiating speakers along the side walls.

For a 7.1 system, the most popular route is to have a pair of the QS series surrounds to your sides, slightly above the listening area, and a pair of direct radiating rears, such as the M2i.

That way you get to enjoy the best of both worlds. The amazing immersion qualities of the QS surrounds, with the direct firing f/x of the M2i rears.