Sawyer, first thing, good choice on the receiver. Next, if you really want tower speakers, I'd agree with 2x6 to consider going up to the M60. However, if it doesn't have to be towers I think that in your size room the M22s would be nearly identical to the M60s above the low bass and would have plenty of dynamic capacity. The sub would take care of the bass. Saving #2 is using a vertical M2 as the center speaker. This would get you nearly all the way to that 45TX, which you can find for a little under $800.
