That “dark and sterile”, is sometimes not a bad thing.... I had the same result with the Mark Levinson No. 35 which received a rave review. It was nicely built but sounded dark and terribly sterile.
(It would certain help to quell a sibilant and bright speaker.)
Unless one is using tube gear, then it is hard to get the frequency response too far out, as amps with feedback are renowned for having low distortion… and flat response from 20 to 20kHz.
Secondly the distortion products are responsible for a lot when amp is sounding sharp and loud, versus when they sound quiet and maybe some people call that dark??
A Jadis set of electronics running into those O/96 speakers look nice and sound good, but I would not refer to the ensemble as objectively low distortion.