I honestly think its a toss up between Denon and Yamaha's amp sections. From all the tests I've read on Yamaha products, a common theme of an overly conservative protection mechanism was at play to limit the power delivery of Yamaha's AVR. It kicked in way too early in all of the reports I've read.
Yamaha & HK seem to put some limits on their 5CH & 7CH outputs, but their 2CH outputs are good.
Power Output 2CH 8 ohms/ 2CH 4 ohms/ 5CH 8 ohms:
$1200 Denon 3312- 143.3/225.5/103W
$1200 Yamaha 1020- 129.2/173.0/73.2W
$1000 HK 3700- 170.2/280.4/40.6W
$580 Denon 1913- 117.7/151.1/81.7W
$550 Yamaha 573- 111.4/126.2/24.9W
$450 Yamaha 473- 96.5/143.2/Protection mode
$350 Denon 1612- 110.3/150.7/78.1W
So even a $350 Denon outputs more power x 5CH than both the $1200 Yamaha & $1,000 HK AVR.
For 2Ch, HK is pretty great. But the 5Ch (40W) and 7Ch (33W) really suck.
Harman likes to advertise their Logic7 DSP, which is like 7CH Stereo mode. But @ 33WPC x 7Ch, that might not cut it if your volume is even a little high and/or speakers are 4 ohms/low sensitivity, etc.