Without having heard any of today's contenders it wouldn't be fair for me to make any judgments, I only know what I read. LOL But in the case of the M28 unless I'm misinformed it is not a pure Class A design like your Krell's Ray, but closer a A/B, so is there a real need for all that heatsink area for dissipation.
Beyond that, on one hand in ultra-audiohiledome we have a contingent using these high rise building amps with claims of them being the true path to nirvana.
On the other hand we have a very large contingent talking up the latest amp techs with things like the Hypex module amps, the new Benchmark ABH2, PS Audio BHK 250, Bel Canto REF600's, etc, etc, etc. Most of those being easily carried with one hand. That side of the isle all claiming to taken amp design beyond the behemoths of yesteryear to new SOTA SQ heights?
We won't even being to include valve designs.
But true be told, besides the huge advances in efficiency design, how far has amp SQ design really moved in the last 25+ years? And in that SQ advancement how far apart can all the latest designs be?
Aren't the monster Class A's going the way of the dinosaur?
Come on over, bring your plate, and see what gets put on it.
Be careful what you say Ray, I just may take you up on that offer and look for a Acourate DRC tutorial while I'm there too boot.