Paimei.
I had the original Pass X600 monos from about 1999. I thought they were somewhat cold and unmusical and that did not seam to change with time. Some say these amps are warm? They did have lots of detail or was it just lots of brightness. They also had a nasty habbit with turn on and off thumps. Something that scares me and something $17K amps should not do. (do Pass use any protection at all?), They did eventually ruin a spekers voice coil.
It would be interesting to hear some of the big monos from MBL, Griffon, Symphonic Line, FM Acoustics, Goldmond, even Classe Audio has the big Omegas. I bet very few people have spent any time with any of these (me included).
I bet a much smaller tube amp would proove to be better sounding at a fraction of the price.