Mytek slams Hypex in Stereophile Amp Review

One of the very interesting and best things about Class D is that those modules can be made modified and made proprietary by engineers.

I'm not so sure about it being possible to modify the modules themselves. I believe that they are pretty fixed.

Perhaps the module makers (Hypex, ICE, TI, etc) could tweak the switching frequency for a company like Mytech to impose a house sound, but Class D is high tech and boutique amp makers don't design semi-conductors. 

Where the boutique amp makers get to play and differentiate themselves is with the case, power supply, outputs, and possibly a pre amp.  

I'm not so sure about it being possible to modify the modules themselves. I believe that they are pretty fixed.
Definitely possible - Rogue does it.

Rogue adds a tube input stage to sweeten the sound from the Class D output stage. This is a good example of adding a house sound.

Boutique amp makers are under a lot of pressure to differentiate their products from the module, which is also branded. Ice has bundled a power supply with the module, leaving "amp makers" scrambling to find tweaks for the copywriters to wordsmith. 

Things are changing though. Module makers realize that boutique amp makers want more control so they can impart their house sound. Hypex has a module that they won't sell to DIY.

 Anyway, it's interesting to sit on the sidelines and watch a newer market develop inside of our dinosaur hobby. ;-) 

Seriously, the Class D are amazing these days compared to even 3 years ago.

This is quite possibly true, however it is hilarious that people have been saying this about Class D for the last 20 years. 

All these class D companies utilize modules from several main suppliers which they modify to their own tastes... Yet, NuPrime manufactures their own modules and is the best Class D I have heard with the NuPrime ST-10. And, that is not even their best. People overlook this company not realizing they stirred a lot on interest in Class D when they were NuForce, now NuPrime.

NuPrime does not manufacture their own modules. When pressed on who their supplier for modules was, they refused to answer. That does not mean that they aren't actively involved with the engineering types of decisions. It just means that they are not a semi-conductor company.