Speaking of driving 4 ohms; the Audioholics review of the 601 linked to earlier in this thread is used with Axiom M80s as reference speakers and no dificulties were encountered in driving them.

How cool is that!? Onkyo is not often refered to as being a normal candidate for successfully driving M80s, but in actuality they work just fine!

Kinda like the Clark Kent of the receiver world