Hi Nick,
I saw Clint's review and it's encouraging that the SR601 did not shut down. On the other hand, if Clint didn't bench-test the SR601 into 4-ohm loads to determine whether or not it goes into current limiting, then it's anybody's guess as to whether it's driving the M80s with 30 watts per channel or producing its rated output.
A 30-watt-per-channel output (or less) is what would result if the Onkyo used current limiting with 4-ohm loads. That amount of power output would still drive the M80s but leave no headroom for dynamic peaks.
Previous Onkyos reviewed and bench-tested by Sound&Vision magazine would automatically go into current limiting, severely restricting the power output into a 4-ohm load.
I also find Onkyo's quoted amplifier output specs for the new model do not instill confidence that it would drive M80s without restricting its output power. If Onkyo can't quote a specification for driving a 6-ohm load across the musical spectrum from 20 Hz to 20 kHz (a 6-ohm load should NOT be difficult for a decent amplifier section) and must resort to doing the test at a single frequency (1 kHz), which is a much easier test, it suggests that the power supply has significant limitations.
Regards,
