I tried the Nordost Blue heaven, Canare 4s11, ridge st audio Poeima and the nordost seem the most synergistic so far. Amps were Mc2275 and Arcam receiver.
I actually find the tonal balance and smoothness of the Harbeth very satisfying. It is not the last word in detail and the treble could be more open. The Nordost balanced them nicely. If there are success with other cables, I certainly like to try.
My other speakers are Avalon Diamonds & Quad 2805 and I still enjoy the Harbeth m30 tremendously. I like the M30 more than previously owned Cremona auditor, thiel 2.4, 1.6, Proac ref8s signature, spendor s3/5se. Harbeth is not instantly impressive but it proves it's worth after some mileage.
The only speaker that I remembered enjoying as much was the B&w 805S, That was when I first got my first pair of "hifi" speakers. I have no idea if I 'd like them now.