... M201 has no claims to being a reference product. Rather, it was JRDG first ICEpower amp .... Hence I am not at all surprised if you much prefer 8T over M201....
Unfortunately I've never listened to neither the old school JRDG nor the most recent 623.
Instead, I've listened a number of times to the Capri+201 combination and I was disappointed by the sound. Not objectively bad, but a side by side comparison with the Copland CTA405 (which I then purchased) had the Danish a clear winner. And the speakers were B&W 804S, which, theoretically, should had favored a SS design.
In the end, the 201 was just a Rotel in a luxury case.
A more interesting comparison within the JRDG product line may be 8T versus M312--M312 being the most mature and state-of-the art stereo amp of that company's ICEpower phase.
How does the 312 differ from a 201 (apart of stereo vs mono and the power difference)? The two IcePower modules in the 312 looked the same as the ones in the 201...
In any case, a reference product which is essentially composed of a circuit conceived and produced by third parts is not my cup of tea, rigorously IMHO