Just so you know what the others are talking about regarding the impedance switch read this excellent article. It will explain it all in detail.

http://www.audioholics.com/education/amplifier-technology/impedance-selector-switch-1

Also, if you have the M80's set to large in the bass management settings, change it to small and use a higher crossover point. That will definitely help take some load off the AVR as well.

I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne