I took my Pass XA160.5 over to a friend's house to compare the Pass XP-30 to the Ayre KX-R(?). They both sounded excellent, but if I were to buy one, I would choose the Pass pre. It was slightly smoother with less emphasis on the high frequencies. They seemed equally detailed, but the Ayre seemed slightly tipped up. I would describe the Pass as neutral or slightly warm, where the Ayre was definitely on the cooler side. The Pass seemed just slightly better balanced to me, though I'm sure others would hear it the other way around.
I own the XP-20 which is also excellent, just not quite as refined, smooth and detailed as the XP-30.
I own the XP-20 which is also excellent, just not quite as refined, smooth and detailed as the XP-30.