I built 3 Gan stereo amps from Gan Systems boards and a Starcrimson set of boards.
ASR had their typical reviews of Gan Amps which really has no listening / sound metrics. The Gan systems boards have the ability to turn off loop feedback and I preferred that vs the feedback even though it "technically" has a lesser spec.
I had several SS amps I owned at the time and sold all after getting the Gan amps. Gone are my Levinson 333, Burmester 956 and Telos 200. I kept 2, The Symphonic RG1 mk4 and a clone DartZeel. Â
The Gan amps I have heard at shows as well as the ones I built all seem to have a family sound. They have the atmospheric envelope that tubes get with low level detail clarity that tends to get lost with a lot of SS. The Gan amps are cool though, like a 6922 run with plenty of current vs the lushness of the 6sn7 octal tube family.
I have a DHT preamp based on the 201a which is not commercial but if I were going to get a commercial preamp for the Gan amps it would be a good 6SN7 based unit that has a bit of body. Dodd made awesome preamps w 6SN7's if you can find their Reference unit it is world class!
With your speakers and the clean lean Gan amp you are going to want a 6SN7 based preamp. If you had KEF's then a SS pre would be ok.