You want pro advice?
Well Alan is on vacation but if you can stand some amateur advice, then you're asking the right people.
Your present selections sound excellent. You could go with either the towers or the bookshelf style speakers for a room that size but i would not recommend the M60s or anything larger. My own room is of equal dimensions and i've found it a real pain to get them tweaked right. The smallish sized room makes it much harder to move the speakers around and create a really good, wide soundstage.
If you are interested in keeping the cost down, go with the M3s route with a sub and do the Axiom 30 day audition. If you prefer a larger sound after you've heard the speakers, then consider returning the M3s within the 30 days (full refund) and order the M50s.
If you don't like the Axiom sound at all, return the M3s and you will need to start shopping around again.
Just to note, before too many jump in here, the M2s (and the M22s but possibly beyond what you want to pay) will have a slightly more detailed upper end (higher sound frequencies) over the M3 but the M3 produces a tad more in the bass department.
