Welborne Labs Star Chief 45

Hi :-)
Based on recommendations in another thread here (Amps for Avantgarde Duo), I have been looking around for smaller amps than my 845 monos.
And, I have had a pair of Welborne Labs StarChief 45 monoblocks in-hosuse for two weeks.
They hadn't been used for some months, so they did actually need a period of burn-in.
They have TJ Mesh Plate tubes (as standard).

The sound is very open and detailed, the upper frequencies are better than in any amp I have heard at home.
The mids are also very good, and the bass is very surprising!; faster and more detailed than in my 845's. Not quite the same weight though....
Until now I like them very much, they are very musical and involving. And more neutral than all other tube amps I have had in my system.

Anybody having any experience with these amps?
Anything "missing" which might become more evident after some time in use?

I will also have the opportunity to test out a WL preamp, the Ultapath BP. Anyone knowing this?
I have a BAT VK-51SE which plays very good with the monos, but the synergy effects between the 45's and the Ultrapath might surprise me.........

Best regards