I use the Arcam AVR100 and P85/3 in my system. The A65 will probably not give you enough headroom to drive the M80s to satisfying bass levels with movie soundtracks (assuming you have mixed HT/music needs). On the other hand, the P25 is rated to something like 23 amps of current, so power is a non-issue for you.
Arcam amps sound fantastic with just about any speaker you throw at them, but the better amps are quite crisp and transparent (compared to Anthem, for example). The M80s may be a little bright. Unless your room is monstrous, the M60s will sound great with Arcam gear.
