Hi Mojo,
Excellent testing and I'd agree with you that the Denons, even the inexpensive models and the Sherwood Newcastles will drive the 4-ohm M80s without problems in average-sized rooms.
However--and it's a big "however"--you would really have to put an oscilloscope on the output and monitor the audio waveform to see when the Denon approached or went into clipping. I suspect that may be happening because our detection threshold for distortion with music and soundtrack material has to reach quite gross levels--from 1% to 3%--before we notice a grotty, edgy or nasty edge to the sound quality.
Psycho-acoustic studies have demonstrated this repeatedly. I'll be writing about this subject in an upcoming newsletter article, but what's surprising are the momentary peak power requirements in some music that you'd think wouldn't be demanding.
It's a matter of acoustical "ease" at loud listening levels, even with smaller loudspeakers when they're fed unlimited amounts of power with no clipping. I was testing some Axiom W2 in-wall/on-wall hybrid speakers driven by two older Denon Class A/B monoblocs rated at 250 watts per channel into 8 ohms with no subwoofer running--the tests were double-blind so I had no idea what I was listening to until after the test. I couldn't believe how clean and loud the sound was and how much good bass there was from the two W2's unassisted by a subwoofer.
Later, the tests were repeated again with several different and excellent subwoofers mated to them and the same Denon monoblocs driving the W2s. I wrote down comments like "excellent"; "really transparent and clean"; "very natural and uncolored", "wonderful deep and powerful bass", and "these are great speakers--what am I listening to? M80s, M60s?"
I was amazed that the satellites in these tests were W2s and I attribute my comments to the large amounts of unclipped power (and of course the inherent quality of the W2s).
Regards,
