Proac response D2 or Harbeth for a Leben cs-600

we still don't know what the current speakers are.

Charles1dad,
If it's a "cliche", maybe it is because many people feel that way. There are many ways of approaching anything, but it still seems to make more sense to choose the speaker you like best, and then the amp that brings out the best in that speaker.

FWIW, I once owned a CS-600 (great amp, IMO), and I took it to a Harbeth dealer to listen to it with the M-40.1. I was unimpressed, as was a buddy I brought along (and was the dealer from all I could gather from his non-reaction to the experience). The resulting sound was flat, lifeless, and not involving. It sounded like average solid state.

On the other hand, I owned at the time Castle Howard II loudspeakers that were absolutely magical with the CS-600, creating an amazing three dimensional image that was extremely fun to listen to, if not the last word in control and resolution.

Concur with Charles1dad.

To the OP, if you prefer your sound on the heavier, bassier side of things then Harbeth's are less likely to deliver.

Devore speakers have been suggested in the past as a musical match ... maybe worth considering also.