Tube preamp for pass labs ?

I recently bought a brand new Pass Labs x250.8. It seems to be finally broke in after about 800 hours. I’m using a good preamp, the BAT VK-33se. I’m curious what other tube preamps others are using with this amp? 
one thing I did was bought inexpensive Wireworld stratus power cables on Sale for $116 shipped brand new for amp, preamp, dac, and server. They seem to have helped settle my system down quite a bit. I really like these inexpensive cords. 
but, again what tube preamps are you owners of the 250.8 using?

TIA for any info given. 
Starboard