I have both speakers, and generally agree with consensus opinion that the M3's have a little more bass, but the M22's are more accurate. I would go with M22's and build on that, because the M3's are not going to satisfy a bass head on their own anyway.
I am running the M22's without a sub and they sound just fine, although very little rock gets run through the M22 system. They don't punch you in the chest like a subwoofer would, but especially with things like Jazz they do a fine job on their own. I can hear the bass hits in the basement, so it's not like they are totally anemic.
I would suggest that not any sub will do. A cheap sub will give you the punch, but you will diminish the accuracy of the system. You should mate the M22's with an accurate, musical sub, which will be a little more spendy.
