My experience with M2 and M22 is that they sound very similar and as John mentioned the M22's do play cleaner at loud volumes, that would be to say the M2's sound strained and the midrange becomes less clear. IMO,the M22 does have an ever so slightly smoother sound, which I suspect is due to the slightly lower FR it has.
I suspect you might be wanting better upper bass where the M22s have an edge over the M2s as John pointed out but the M60 or M80 would be my suggestion for an upgrade.
Something else you might want to try, if you have the room, is adding the VP180 (or wait for the VP160) to the system which will add a great deal more sound/warmth/texture to the front soundstage for movies. I briefly tried a VP180 with my M22s and it worked very well and I felt the movie had more punch to the action scenes.
