I own the Pass Labs X2.5 and it is superb value for the money (about 95-98%) the performance of the much more expensive reference X1 model (same internal circuitry other than the power supply). It is extremely quiet and very neutral- lets the music come out. You are not going to get the midrange magic with the top of the line Conrad Johnson, Audio Research or Jeff Rowland, but for less than $4,000 ($2,500 in the used market), you cannot find a better pre-amp for the money. The looks with cool blue lighting and industrial style finish is a bonus (built like a tank and never looks outdated even 10 years later!). I have auditioned it in the shop with a mega high-end set-up including a Classe Omega SACD player, Pass Labs X350, and Gershman Acoustics Opera Sauvage and the sound was glorious. I heard it in direct comparison to the Classe 47.5 and 65 and find the 2.5 much more detailed, and transparent with better control of the music. The soundstage is very broad with pinpoint accuracy for musical images. For me, it was a no-brainer.
Musical Cheers!
Jason
http://www.martinloganowners.com