Alex, welcome. No, the M60s certainly wouldn't be too much for that size room; you're in control of how loud the speakers play, not them. Since you're considering two fine subs, the advantage that the M60s would have over the M22s in the lowest bass wouldn't be relevant and the advantage of being able to play at very high levels a little more cleanly than the M22s wouldn't likely come in to play at the levels that you'd be using in that room.
My experience with the M22s and EP500 leads me to suggest that the M22s plus the sub that you're considering would give you excellent results and that you should go that way unless you have some other reason for preferring tower speakers.
You don't mention it, but you should certainly consider getting surround speakers, preferably QSs, for use with all your source materials.
