Jack, as Randy mentioned, it appears that the main question should be not whether a 4 ohm speaker can be driven, but rather how loudly. There's a tendency to overestimate the amount of power actually used in home audio and also the difficulty with 4 ohm speakers, since if the power used isn't high neither is the current, even with 4 ohm speakers. The relatively new 2700 doesn't appear to have any lab tests yet, but the 2600 has tested very well, including into 4 ohms. The S&V test
showed over 200 watts into 4 ohms. The 2700 should be plenty for the M80s in most setups.