Someone had the 875 around here, because we were comparing it to the 806. As I recall they were really happy with it (and the specs seem to support that impression) but I don't recall the speaker - but odds are it was the M80. Search the forum for 875 and you should find some comments that ease your concern. I was looking at the 806 and 875 and came away satisfied the 875 would handle my PSB's which, like the M80, run down to 4 ohms sometimes.

Hope that helps.

Panny 3000 PJ, 118" Carada, Denon 3300, PS3, Axiom QS8, PSB 5T, B&W sub, levitating speaker wire