Nathan, welcome. In your size room the M60s should be plenty, although the 2600 should handle the 4ohm M80s as well with no problem. Incidentally, the 400 watt maximum power rating on the M80s and QS8s isn't of any particular significance in actual use. In theory it represents the power which could be input continuously without the speakers going up in smoke(the M80s have actually been tested to over 1,000 watts), but doesn't indicate anything about the power which is really used, which is 1 watt most of the time with brief peaks possibly in the 100 watt range. So, the 2600 is well-suited for use with any of the Axiom speakers.
If you want to use a horizontal center the VP150 matches well with the M60s, but my own preference is for a vertical center, such as the M2.
