Which Class D Amplifier? PS Audio, Ghent, Nord, Merrill or other???

Check out SPEC of Japan. I absolutely love my SPEC RSA-717EX. Beautiful tone. There are a handful of dealers in the US, I got mine from Pitch Perfect Audio.

SPEC makes a few different models but the house sound is the same. Jeff Day nails the sound in his review:
https://positive-feedback.com/Issue78/spec_realsound.htm

Jeff compares/contrasts the SPEC to a Leben CS600 and as an owner of the CS300 I can say his comparison is spot on.

The people who say "oh, class D, been there, done that" haven’t heard everything.

Your answer begins and ends with Digital Amplifier Company. 
https://www.cherryamp.com/

His design is fully proprietary, & refined forever. It's not Ncore, it's not Ice, or B&O or whatever.

He only sells direct, which is why you don't hear much about them apparently. I myself own the 'classic cherry.' Bought earlier in '18. Best amp I've ever owned and I've owned a bunch. 

singintheblues
Which company is producing the best sounding Class D?

The only Class-D's so far that to use the more advanced GaN semiconductors for superior dead time and higher switching frequency that will give better sound. 
Are the Technics SE-R1 and the other is in your list, the Merrill Audio Element 118 monoblocks.
It won't be long for this technology to filter down to more affordable Class-D amps so be patient.

Cheers George