Mark, the M2s would be fine for mains if supported by one of the relatively inexpensive subs which are available. If the center speaker isn't centered on the TV(dialog and other TV material wouldn't image from the center of the screen), but instead on the 12'x 16' listening "room", it'd sound better for other than TV listening. Also, there'd apparently be room to place a 3rd vertical M2 for the center.
As to the side surrounds, if the couch is going to be fairly close to the rear wall(say, within about 4')mounting on the rear wall about 6' up and separated widely enough to be outside the edges of the couch(could be as wide as the mains)would give good side effects with some "phantom" rear support. QS4s should be excellent.