The M3ti, M40ti and M50ti have consistantly been grouped together as the more "laid back" sounding Axioms speakers.

The M2i, M22ti, M60ti, and M80ti, are the more forward, detailed group. If you have and enjoy the M22ti, the step up the food chain for you would be the M60ti, if you want to keep the same "style" of sound.

How big is your room? How far away would you be sitting from a pair of towers? How close together would they be? Depending on your room, and setup the M60ti's aren't necessarily going to be "better" than the M22ti's you have now. The bigger speakers need more breathing room.