match tube preamp w/Pass X250 recommendations?

what are some good matching (impedance?) tube preamps (balanced) for use with a Pass Labs X250.
I'm not into tubes but I use my X250 with an Aleph P preamp. The Aleph stuff was always described as solid state for people who like tubes. Pass Rules!!
For the past year, I have been using a BAT VK 30 preamp with a BAT VK D5 CD player that worked very well together. Before I used the BAT preamp, I was using an Adcom SS preamp. The BAT preamp opened up the soundstage quite a bit when compared to the SS Adcom.

A couple of months ago, a friend allowed me to audition his '60's vintage McIntosh 240 tubed amp as part of my system, and I found I really enjoy the sound of a tubed amp.

I have decided to go with tubes all the way. I sold my Pass amp yesterday and have made an offer for a BAT VK 60 amp (tubed). I guess my point is, you may find once you start using tubed components, you may wind up with more than one piece.
I enjoy my Cary Audio SLP2002 preamp with my Pass X250, balanced XLR interconnects between them. No problems with Z match. I also have a Cary 308T CD player sporting a tubed analog gain stage. The Pass amp mates very well with these tubed components, makes my big Magnepan 3.6R's really sing. The tubes add just the right amount of warmth and seem to eliminate any digital grit and grain. Big Maggies love power and the Pass feeds them very well indeed.