If SINAD is the only thing that matters to the individual, then I bet there are cheaper alternatives like the Chinese amps. Just like if FR is the only that matters, then there are cheaper alternatives to high-end speakers. I bet Chinese speakers can have great FR too.
There’s an amp and speaker and car and house for everyone.
Yes, I only mentioned SINAD, but if you look at the other metrics on ASR bench test results, you could hardly find anything that it would not do better than the previous benchmark for power amps based on specs/measurements

, i.e. the Benchmark AHB2.
Here's one SINAD vs output graph, but not single point, instead, it is for 20 Hz all the way to 15 kHz, as Amir commented, essentially no frequency dependency!!
Topping LA90 Discrete Amplifier Review | Audio Science Review (ASR) Forum
and it beat the Benchmark amp significantly in output vs SINAD too, if used within its rated output:
and then the huge dynamic output:
That is, for a 66 W rated amp!
Would I buy such a class AB power amp, hell no, but not because it is Chinese made, discrete, and/or bench test measurements, SINAD, FR IMD or whatever, but simply because I want to have a lot more rated output than what I actually need, this Chinese amp is not going to do it for my speakers in my room, though practically speaking, it will do the job, but again I want more, say about 4X my actually need would be a good starting point.