Chris, a separate center speaker has the advantage of keeping the center image fixed for off-center listeners(the phantom image shifts as the listener moves to the side). It also has the advantage of making the center channel volume adjustable independently of the mains, which would allow for increasing the level to help with low-level dialog.
Be that as it may, the phantom center can be satisfactory in many situations, and my view would be to instead look first to improve the surround sound. With the M22s I wouldn't think that the best effect would be with pointing toward the front(as the left one is in the picture), rather with them pointing inward toward the couch, or even backward for a more diffused surround.
If a change in speakers will take place, my suggestion would be to trade the M22s in for QS8s.
I assume that you have a compelling reason to keep the present diagonal arrangement rather than placing the fronts and TV along the wall to the left.
