What tube pre-amps pair well with Pass amps?


Does anyone have experience with this?  I'm running Focal Sopra No. 2s and I understand the Focal's pair nicely with Pass amps.  Any tube pre-amps you'd recommend for consideration? I like the classical rock, but am gravitating more to jazz, classical and vocals. I just want to try something new.  Thanks.
billtro
The LSA website recommends speaker sensitivity as:

Critical listening environments: 105db sensitivity and above

Smaller rooms / lower volume levels / non-critical listening: 97db sensitivity and above.

Aren't those levels speaking to horn speakers? 

KR is a Czech company which helps keep the prices down a bit compared to Germany. They are best knows as a premium manufacturer of tubes and their Kronzilla power amps.  

I sell a lot of their tubes.  Quality is extremely high though as odd as it sounds, the KR amp does really well with EML 45s.  KR tubes are best when the current can be increased when biased which doesn't happen in a preamp.  

PM me if you want to discuss pricing.  
You've got a smattering of responses and I'll add mine. When looking for a pre to pair with my first watt f4, I read a lot about tubes and topologies and eventually settled on 6sn7 based units. If you want a balanced design, I'd look at atma-sphere's offerings. For single ended, I was choosing between de Havilland, Don Sachs, and supratek. I eventually ended up with the Don Sachs and it improved everything about my system performance. Didn't get to demo the competition, but from the reviews, I don't think you can go wrong with any of those choices. The 6sn7 is nicely linear and sweet. I'll probably still try out a supratek at some point...