The total power supply draw is less than 300W. So there is no way that the 1222 puts out a full 600W at any time. Now because of the very efficient class D you are using 240 W of the total available @280W whihch is incredibly efficient. You can confirm this by checking your power supply where your power cord attaches.
It makes sense that with a more efficient amp it can have a similar Watts/channel rating in STEREO when compared to the 600W power supply Denon 2313. For instance the Denon 2313 has a 600W power supply but in stereo puts out 105W/channel=210Watts=390 Watts in efficiency losses. I am going to guess that the Peak power of the Denon is much higher but RMS is going to be a better guide.
I have the same question: I do not have a 4k TV, but I would like to use my 2nd zone. I just bought the 2313, but for $15 less (basically equal) I can get the 1222. For me the answer is in sound quality, but I a cannot find a place that has both a 2313 and 1222 on dispay. Frustrating! and my local Hi-Fi shop which is the only place that carries the full like of Martin Logan speakers I want to try in store only displays Yamahas. SO I have no clear comparison.
If you wer 50% movies and 50% music, and you were not planning on buying an amp (Pioneer has pre-amp outs) or 4K TV (Denon has 4K pass through) for at leat 5 years and the speakers you were planning on were 4 ohms which one would you buy?
Bottom line, I like that it runs cooler and has the manufacturer will warranty with 4 ohm speakers, but will does the class Ds lower distortion level actually correspond to higher fidelity music to the ear?