second to Sugden amp suggestion.
I have Naim Supernait 3 integrated driving a pair of Spnedor SP2/3R, Esoteric SA50 SACD/CD player. I only just got Naim recently which replaced my Moon 240i and before that I had Plinius 8200 mk2. Like you I listen to many types of music, but I am a violinist, for years I have been trying to sweeten the treble (Spendor's treble is not harsh at all) and yet I worry I might lose that organic and natural sound. However Spendor for me is laid back, if money is no object, Plinius and flagship Moon integrated can do powerful and organic, I simply can not afford to play the upgrade game with those brands.
Since you already know Naim sound, why not audition Supernait 3?
Naim Supernait 3: after running in for two months(around 400 hours), this amp plays loud! I rarely get to 9:00 in volume. In the first week before it settled down it was actually more dynamic and raw, now it's got smoother with good control in all the departments. I worried it will improve the dynamics but treble will be too hot, but Classical music actually sounds pretty smooth. The only thing is soundstage Plinius is definitely better. Sound quality is really good, it makes Spotify sounds better(I have tried Spotify, tidal and Qobuz)
So some of amps that come to my mind
Yamaha A S3200 or AS3000
If the a very good "Hi-Fi" sound is what you are after then there are a lot amps out there that do it. But there are brands that go a little extra, not just clear and detail sound, for example, some amps have "soul" especially if (you are musician) you know the sound of certain instruments very well, probably quite picky about the timbre, see if you could audition Luxman, Sugden or Yamaha. I heard Accuphase as well, amazing amp but it's really expensive but it could be your end game amp.