Well guys, I went ahead and got hold of a 250.5. While I don't have a pair of JC-1's on hand to do a direct comparo, I can give a little feedback as I used to own them (though we all know how tricky "audio memory" can be, so bear this in mind while regarding my comments).
I think they are both very similar sounding amps - both great! It probably would come down to system matching, and also in some installations, a single chassis (250.5) vs. a pair of mono-blocks (JC-1). But again (he says carefully as he steps onto the thin aural ice..) to my memory, it seems like the 250.5 is a bit more relaxed sounding, the same impression I stated earlier. Maybe this is due to the fact that the 250 runs more watts in true class A mode? I'm not sure. Also the highest frequencies seem to be a bit clearer and grainless compared to the JC-1's, but again, I'm stepping a bit into the land of aural conjecture.
Anyone who lives in reasonable proximity of northern Ohio (who owns the JC-1's) can contact me so we can play a little audio shoot-out. I have a friend who lives in southern Ohio, and owns the JC1's, so when the snow clears (and if my lower back can handle moving my 250.5 again), maybe we'll arrange to do a head-to-head. He has a "killer" system with SoundLab M1's, Meitner, etc. so this would be a highly resolving comparision.
Will keep you all "posted".
BTW Rapier21 - the only spec I can find relating to how much Class A the 250.5 puts out, is from a review I found on the 250. It says somewhere around 80 watts before switching to A/B. Your right about there not being any reviews on the 250.5, but there are plenty on the 250
www.positive-feedback.com/Issue6/pass250.htm
http://www.enjoythemusic.com/magazine/equipment/0202/passx250
http://www.theabsolutesound.com/articles/tas133_cordesman.html
