Upgrading pre amp advice.

Since you are in Europe, how about something like the SPL Elector. It is in the same spirit of the smaller brand Bryston, pure SS analog with a retro flare to it, and reasonably priced. I was considering this one, but discovered it only after ordering something else.

https://spl.audio/en/spl-produkt/elector/

Look at this absolute sound review.

https://youtu.be/NMcIE3K2bD8?si=v5IAb0hVbfJE3wHe

I love my LTA level 3 preamp. Others that I’ve owned and recommend are the Holo Serene KTE, and Audio GD pre with the built in regenerator. I had the tubed version but you can get it solid state as well. Also had the Sachs pre and while I liked it I didn’t like it as much as the ones above. Also had a Grimm MU2 and while the dac is great I think it’s pre section is the star of the show. Saying that because I fed some other dacs into its preamp in and a/b’d the internal dac with my external dacs and there wasn’t a huge difference. But when comparing the pre section to my Holo Serene, which I loved, there was a noticeable difference. 

If you must use a Class D amp, your depth is handicapped. So I’d look for a tube pre. 

I know if I were in your position I would sell/trade-in your DAC and preamp for a DAC with volume control. That is, if digital is your only source. The value and sound quality is way better that way, in my experience.