Never owned both but have compared them as I do own the M22s. I wouldn't say the M22s have an advantage it is just a different sound. The M22s are much more forward than the M3s, the vocals and mids stand out from the bass more so than the M3s, making sound clearer or more detailed depending on how you want to describe it, adding a sub to the M22s just fills in the lower end they don't play. I have my M22s as a 2 channel setup and it sounds very good, not thin at all, but I do run the bass boosted by a couple of db and it does give them that warmer feel of the M3s with the extra clarity only the M22s have.
If you truly want better sound, I would save up for the M60 or even a little more for the M80s, both of which work much better for large rooms and have a fuller/richer sound that the M3/sub or M22/sub doesn't have, IMO.
