In fact, I did turn the rears off and listened to the same scene. The QS8's gave the impression that the sound was behind, but the M2's made it much more precise in my room. It may have to do with room acoustics as you say. On one side of my room, that's where the entrance is. It's a wide open hall leading to the stairs, so no rear wall to bounce the sound off. That's probably why any type of rear speaker would be better with rear sounds than just side QS8's.

"Not throwing my hands up or my dress above my ears don't mean I ain't awestruck." Al Swearengen