There's another angle that we have to consider.
The SPL out of speakers doesn't climb indefinitely. Just because the M80s are rated to 400W, that doesn't mean they don't saturate from an SPL stand-point well below 400W. All the power that goes into them after saturation simply gets converted to heat in the voice coil and filter network. And the room saturates as well. So I don't understand what the "extra" power buys anyone?
And the other question is what does that 400W really mean? I bet I can easily put 400W of complex power into the M80 with my cheap Denon that is rated 90W/channel. At 50Hz (the frequency at which the M80 experiences its impedance minimum), my Denon need only source about 7.5 Amps (real + reactive) which I'm sure it can do. Now as to what it sounds like at that level is an entirely different matter.
I think I'll try this tomorrow to see what happens.
