As I said, NC400 - is redundant solution. When you are in search of minimal distortion from your amplifier, you must not forget that the main source of distortions - your speaker system - 1% 2% 3% ... even if you have good speakers.
But this fact prefer to forget brands like HYPEX. All these results of laboratory measurements - no more than a marketing ploy.
If you are not satisfied with ready-made solution and you want to build your own power - turn your attention to IRAUDAMP7S from Infineon Technologies, this solution is significantly cheaper, so, I repeat, you will not hear any difference in the sound.
As for my personal preference, HYPEX I do not like, because, in addition to amplifiers, they trade audiophile cables 200-300 dollars. It seems to me a serious chip manufacturer will not trade audiophile cables
Therefore, in my personal taste, Infineon Technologies - this is much more of a company in terms of technology than HYPEX. Earlier Infineon Technologies company was a division of Siemens AG Semiconductor Group.
P.S. More information about the amplifiers based on IRAUDAMP7S you can look at the channel
https://www.youtube.com/channel/UC2yDSO46soRXRvQyhOfKr9Q/videos