I thought the 805 had been rated for 4 ohms. I think you'll be fine, as the M80s are supposedly considered a light 4 ohm load, and the new Onkyos supposedly have better amplifiers than in the past. I think the only reason I'd return the 805 is to go to the Denon 3808, which is a little above your $1000 budget.
I tempting to try Denon. Local store Best buy carry 2308 for $900. Let us know about the sound quality/bass performance. I like Harman sound excellent when I paired with my Axiom speakers. It's something in those Harman sound. Wish Harman can build their products close to Onkyo and Denon.
