I know everyone loves the M2, but I think the M22 is always the better choice; it has the same "sonic signature" and doesn't drop off the map at 70 Hz (in the non-OW model, there's no specs for the OW). And I wouldn't rule out the M5OW either, even for the 9x10 room. I'm currently using three M5HPs, two Advent mini surrounds, and a small sub in a 13x14 room and it's not too much at all. So I don't think the M5OWs would be out of place in the OP's room. And avoiding the sub could be nice if it's going to be a music system, or just to reduce space requirements in a smaller room.
Also, the M5 (HP or OW) is rated at 8 ohms, so any standard receiver would drive it; even though it dips lower from 100-500Hz, that's taken into account for the overall rating (so Mojo, you have to explain yourself on that one). I've having no problem driving the M5s and mini-Advents now with a Yamaha RX-V681, and I've used an RX-V673 in the past.
