I upgraded my M50s to M60s and M3s to QS8s - I can sympathize. I've never heard the QS4s, but I'd been using the M3s for surrounds and they were fine. When I fired up the QS8s I was in awe - sound came from all around.
I played the beginning of Toy Story 2 and the scene where Buzz is flying through the canyon in the video game, the camera moves to his viewpoint and the sound of the rocket came from behind the couch. The QS8s are mounted above on either side - great effect!
I'd say *IF* the QS4s don't do what I described, I'd lean toward those, with movies, it's mostly music and effects coming out the mains. If they do, it's a toss up. Good luck, you've got a tough decision.
