What tube pre-amps pair well with Pass amps?

Check out the KR P-135.  Has XLR ins and outs.  Review at positive feedback is glowing.  
Full disclosure I am a KR dealer but I think it would be a cool match.  

Scothurwitz

Thanks for the reply.  I'm currently running Prima Luna Dialogue pre-amp and 2 HP amps as mono blocks, which I intend to keep (read tube rolling fun) in a 430 square foot room.  The PS audio pre-amp has been on the screen, as I have their DMP and DAC.  With this matchup, do you think the Pass Labs XA 30.8 has sufficient power for the Sopra 2's?  I've always been intrigued by Class A amps and its on my bucket list. 

One last thing, do class A's handle sub-woofers? 

Thanks for the lead VERDANTAUDIO.  German company?  Its a big world out there.

The most helpful information you could provide would be what sound qualities you value and/or would like to improve upon.  Without that this is really just a shot in the dark. 

SOIX, you are absolutely correct.  I've just relocated and am in the process of addressing my new room's acoustics.  Treatments are on order and until I get the set up I won't really be able to tell where I'm at.  Until then, I'm just searching for possible ideas.  Since my current system is all tubes, I'd like to explore SS with a little more slam for complex and/or dynamic music.  

Thanks for your reply.