But wait Peng that really doesnt address the discrepencies I cited. First of all, for Denon who has every motivation to rate their amp as highly as possible to record their product as doing 160w into 6ohm at 0.7% thd, and for unbiased reviewers to state that the same amp does 279w at FOUR OHMS with 0.1% thd is not a small or negligable difference. It also makes no sense at all. How can the same amp that can only output 160w at 6ohm with 0.7% thd also output 279w into FOUR OHMS at 0.1% thd? So that same amp is doing 120 more watts into a lower impedance load while registering 700% less thd. None of this makes sense Peng.
It didn't make sense to you because you seem to be mixing/comparing "specs" and "measurements". You can't do that unless the manufacturers had specified the test conditions fully.
Here's Denon's spec for the 5308CI:
Audio section
• Power amplifier
Rated output: Front:
150 W + 150 W (8 Ω/ohms, 20 Hz ~ 20 kHz with 0.05 % T.H.D.)
170 W + 170 W (6 Ω/ohms, 1 kHz with 0.7 % T.H.D.)
If you look at S&V's graph, at 0.7% THD, the 5308's output would be about 205 W, that's into 8 ohms, so it could be about 220 W into 6 ohms, compared to the specified 170 W.
That's quite typical based on S&V's measurements on other Denon models, that is, their bench measurements always show higher output than specified, by a good margin.
So again, let me emphasized, you can always compare spec between brands/models, or compare measurements between brands/models, but NOT between specs and measurements and between brands/models as it would not be "apples to apples".
Now take a look of the NAD T758 V3:
At 0.1% THD, the graph shows the output into 8 ohms is about 101 W.
The NAD specs say 110 W 8 ohms at rated THD (whatever that means??)
So the NAD's measurements by S&V would show that NAD specified 110 W was optimistic, whereas Denon's (you will find that the same applies to most Yamaha and Marantz' higher range models) specs would seem very conservative in comparison.
I mentioned this because there seem to be some die hard myths that NAD, Arcam, Anthem, the kind of boutique branch (add HK back 10 years ago) published power output specs that tended to be conservative, relative the Denon, Marantz, Yamaha, Onkyo, Sony's etc., when in fact if you look at the bench measurements from S&V, AH, HCC (no longer exist), and now ASR, you will see that the opposite it true. That is, D+M, and Y's are actually much more conservative, so much so that if you compare their specified outputs to bench measurements, they would in fact not make any sense to you.
NAD T758 V3 A/V Receiver Review Test Bench | Sound & Vision (soundandvision.com)
I hope this is now clearer to you, why those numbers don't make sense to you.