I think it is pretty well settled by now that saying "all class D amps sound the same" is about as valid as saying "all class A amps sound the same" or "all tube amps sound the same".
The part that makes it just a little more tricky is the fact that some amp makers do in fact take the premade modules from whichever provider (B&O, Hypex, etc) and throw them in a fancy case with zero unique features. In a situation where two brands actually do use identical guts, like say the same exact turnkey Hypex modules, with no changes or add-ons at all, then they WILL sound identical. This is the equivalent of two class A amplifiers using the exact same internal designs, part for part. Which of course would never happen so the analogy falls apart.
Many or most of the better class D amp designers do things to make their creations unique. Often it involves a custom input buffer with upgraded opamps or discrete designs. Some designers do their own power supply, some integrate a tube output stage, and some make an entirely different class D circuit altogether instead of going with an existing module. All of these methods give a unique result.
All this to say you really end up back at square one just like with any other type of amps. Which means you have to try and get them into your own system to demo on your own terms. If you are trying anything other than the most basic, plug and play designs based on identical modules, you'll get very different results and hopefully end up choosing one which stands out as being the best fit. Anecdotally I would say the ICEpower models are still worth checking out even if they aren't the cutting edge these days. They can still sound great to my ears.