You are right to consider 4 ohm capable receivers - I tried running the M80Ti with Onkyo Integra 7.1 and trouble trouble trouble.

I have not had any trouble at all running them with OUTLAW 1050 with 4 ohm setting on, nor Marantz SR-19ex (thx ultra certified).

The only way I could get Integra to adequatly drive the M80s is when Axiom made for me a speaker conversion box that changed the impedence of the speaker load (CREDIT TO AXIOM - They made it FREE OF CHARGE).