I´ve had my A21Se since it came out 10 years or so ago although I haven´t heard Harbeths. I have never found it hot in the highs but maybe that´s down to my tweeters (Seas Millenniums) and the fact that I have no digital input (ducking). What I do find is that the motorised Alps Blue pot on my SE when used manually as is my case, is a bit " hot", insofar as a Mini Cooper was a bit hot i.e. you just had to blip the pedal and off it shot.
Come to think of it, when I had my A21a and I happened to ask Patrick if a motorised pot could be fitted - this was before I knew how uselessly slow such mechanisms could be, he told me it was not possible with the single-ended circuit, Then lo and behold the SE came out with a motorised pot. I had assumed it was for some electronic reason (power for the motor ?) beyond my comprehension but now I wonder ..... Maybe the motorised pot is designed to respond quickly sonically to counteract the slowness of their mechanical response using the remote . Food for thought,
Anyway, with hindsight an alternative slant would be to use basic but good copper wire (mine are Van Damme Black Tour - 4 core so only one run per speaker) and maybe spend some dough on improving the pot. Despite its seemingly low 30w output, I use mine with a stepped attenuator and also some Rothwells on the input terminals. Much better control. Who knows ?