I don't think you will get the same amazing surround effects if you choose a forward firing speaker only like the m3 or m22 over something designed for surround duty like the QS8. Being that it is a theater room I would think that QS8's would be the way to go hands down.

Check out the 3rd photo in this gallery post:
http://www.axiomaudio.com/boards/ubbthreads.php?ubb=showgallery&Number=206049

As you can see the Q's really blend in and don't stand out much at all.

If you must go with another inwall speaker maybe others can provide some advice as I only have the Q's and have never tried to use m3's or m22's for surrounds.

Good luck!

-David