Scott, due to possible legal liability concerns, in manuals and often even in discussion with company representatives there is an unrealistically cautious approach to operating speakers which are nominally rated at 4 ohms. Amplifiers don't know and don't care what the impedance of the speakers that they're driving is; for a given loudness level they have to supply a certain voltage and current, following Ohm's Law. Any amplifier(as we've learned, even one in a boom box capable of 2 watts or so)can drive a 4 ohm speaker at some loudness level. How loud and how long are the determining factors, not 4 ohms per se.
For most real-world uses the 3808 or similar models from other companies such as Onkyo, Pioneer and Yamaha should do fine with M80s. In the vast majority of cases these receivers are the sensible cost-effective buy, rather than buying two or three separate boxes for the same function.
