The M3 is a speaker that is better without a sub. It is preferred for stereo only listening. It has more bass than the M2 or M22, but the M2 and M22 have better midrange. Because you are getting a subwoofer, the extra bass provided by the M3 will be duplicated by the sub, but the extra midrange of the M2 will not be produced by the sub. The M2 and M22 sound almost identical, the M22 can just play louder. It is unlikely you will ever listen to the M2 loud enough to hear the difference.
I would also recommend looking at www.svsubwoofers.com or www.hsuresearch.com for subs. The only products these companies make are subs and they do it better than almost anyone. They outperform Axiom subs, although Axiom is looking into designing subs that will better compete with these other companies.
I am not saying the Axiom subs are bad, they are still excellent subs on par with subs from Paradigm or Energy. Just that SVS and HSU are unbelivably good products.
