Upgrading pre amp advice.

You are from Europe, so many of the suggestions make no sense as the brands will not be available here. Better look for high-end German, French or Italian brands used, like Symphonic Line, Valvet, Gold Note, YBA. Recently I bought a used MFE Tube One SE preamp for a good price. Couldn't be happier. 

Perhaps, consider having your current pre re-worked?  I see it has tantalums in the buffer stages.  Tantalums are fast, and whoever decided it needs them probably had a goal in mind that doesnt agree with your hearing.  Maybe replace the tantalums with electrolytics to slow it down and give it more musical sound.  If you dont like it you can have tantalums put back

@stievus : I confirm many suggestions are hard or even NOT to get here in Europe so I think I 'only' have to choose from bigger brands.

@logistics : Thx, I was/am still considering this (I am aware of This topic)

@vhond Why bigger brands? All my audiogear is from smaller companies, and 80 percent from Europe. Less overhead, no import taxes, and if I need to know something I just call them or send an email 

@stievus : don't get me wrong (as you can see I myself am using smaller brands): the availability of smaller foreign brands is limited.

I notice many people mention tube gear, not that I don't like tubes but I am not looking for a warm sound (maybe less analytical as I have now). The advantage you can swap tubes to adjust the sound.