I'll take my turn in asking the usual questions...
What is your ratio for movies vs. music listening? For music (if applicable) will it me 2 channel stereo or multi-channel 5.1? (Makes a difference, possibly, with rear speaker choices.)
Are there any size limitations for your speakers, either physically or with your other household members (some people need to check their WAF (Wife Approval Factor) and so forth. If they don't like the way they look, you will spend more time trying to hide them, and thus the sound will be worse than if they were out in the open.)
What type and size TV fo you have or plan to use? Even though I like my M60s, if I had a 27" TV, it would look funny having those sized speakers.
Um, what else.....
You mention room size, but what about any hallways or open areas directly connected to this room? It can impact the size of speakers you need to drive that total air volume. How tall are your ceilings?
These all elad to air volume. For me, I ended up with M60 fronts and a beefy sub because I am set up in my basement that is pretty much one large room, a bathroom and a storage room. I needed to account (according to Alan from Axiom, and I trust his judgement) for the total air volume even though I am physically set up inside only 1/4 of that volume of air. If I made and enclosed room, I woulnd't have needed to push so much air, but I still think that the M60s (for me) were a better choice than my original plan of M22s because I like mid and low range, and you would be surprised how much bass the M60s can kick out (with the sub turned off)...
