Hi dmw,
All of the Sherwood Newcastles that Axiom sells, even the most inexpensive, will drive the 4-ohm M80s cleanly, with no current limiting, overheating or shut-down. We even tried a now-deleted model that was a combo DVD player/receiver, and it worked fine with the M80s.
Ignore those warnings about only connecting 8-ohm impedance speakers. Those are there for liability issues and you'll find that most manufacurers include such warnings, even those whose amps will drive 4 ohms without difficulty--the Sherwood N's, Denon, H/Ks, etc.
I've also recommended the H/K 3480 and as was mentioned, it does list the 4-ohm output specs, a relative rarity these days.
Regards,
