Ayre KX-R or Krell 202 with Martin Logans

"part of a home theater setup"? Are you familiar with the Conrad Johnson MET1?

no not familiar at all with CJ electronics.

If you want the new preamp to be part of your home theater system and integrate with your Meridian, you might want to consider a Conrad Johnson Premier 17LS which has a home theater bypass feature. I have used mine in a combined home theater/2-channel setup and it has been great.

CJ does make excellent tube gear. However, it is single ended which probably won't agree with your Krell amp as well as a fully differentially balanced preamp design.

BTW - I use an Ayre K-1xe preamp with my Krell FPB-600C amp and the pairing produces excellent sound. If the KX-R is a bit forward (not sure that I agree with that assessment though), it should offset the slightly dark character of your Krell amp (assuming it is an FPB since you describe it as the last gen before the cast connections) and result in a very nice tonal balance.