John,
As always, a well thought out and easy to understand explanation.
The Denon amp is a good example. In reviewing my AVR-3806 manual, I see a 7.1A total draw, and each channel is rated 120W. 7.1A x 120V = 852 Watts. 852 Watts / 7 = 121 Watts / Channel. The math works here. The manual also states the amp is capable (dynamic power) of 140W Channel driving 8 ohm loads, and 210W Channel driving 4 ohm loads. This is how I think the EP800 gets rated. The plate on the back of the amp is showing it's 8 ohm load rating, not it's 4 ohm load rating.