Pass preamps file miserably to measure up against their amplifiers. I had both the xp-20 and 30 and they were anemic, sterile, and lifeless when paired with my Pass XA 60.8's.
Yea, that is my experience with an XP-10. I purchased it to go with my 250.8 and I was really disappointed in the overall sound of the two together. I then replaced the XP-10 with a Hegel preamp and liked the sound quality much better. I then replaced the Hegel with a SimAudio 740P and it made beautiful magic with my 250.8. I've since moved on from my 250.8 but the 740P still remains :)