I think your over-thinking the power needs of the M80s. They're very efficient (sensitive) speakers...

The 2809 should be fine, unless you have a HUGE room or really, really, crank it (in which case your old receiver won't do much good and you'll be wanting to add a 200~300 watt amp).

::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::