I fought harsh for a long time. First recommendation I’d have made was room treatment...but you have that pretty well covered - unless there is further benefit to be gained by replacing the decorative blankets behind the speakers with a couple of GIK panels. I found a Hegel H200 SS integrated to be significantly warmer than the 6CA7 tube mono blocks I had. Cardas ICs and speaker cable helped a lot too. A good deal of the pain and "gambling" with wire can be eliminated by borrowing from the Cable Co. I didn’t understand what you are using as a source...any chance this is contributing (or did it sound fine when the Krell was in service)? Finally, I assume everything is well broken in? Final thought is to consider some sort of equalizer. Some here are very happy with the Schiit Loki.
Good luck!
Good luck!