The RR2150 is a stereo receiver, so it has amps built in (rated at 100Wx2 at 8 ohms or 160Wx2 at 4 ohms, so with the 4-ohm M80's you'd be looking at 160W). The M2200's are monoblock amps with more power than the 2150 (200W at 8 ohms, or 300W at 4 ohms), so you could connect a pair of them to the pre-amp outputs of the RR2150 and use them (at 300W instead of 160W) instead of the RR2150's built-in amps. The Model 970, on the other hand, is a surround processor - no amps on board at all, which is why Axiom suggested the 2200's. You could really probably get the RR2150 and use it by itself, and it'd probably drive the M80's nicely, but if you felt that they could benefit from extra power you could always add the M2200's later. Axiom might be able to offer some thoughts on the power needs of the M80's and whether there'd be likely to be much difference between the two approaches.

The RR2150 has gotten great reviews all year, so for a purely two-channel system is could be an excellent choice. I'd have to say that the inability to simply add more amps and speakers to migrate to surround is probably the only drawback to going with it instead of the 970.