Thanks a lot James for this helpful information.
By "Flesh out", I understand you mean you feel the amps have the ability to get more of the THIELs, to go way up to the CS3.7 extreme possibilities ? In other words they like "dissapear" more than with the 7B?? Am I right?
Also, I was wondering if you had any experience in a PASS X1 preamp / 7B or 28B amp combination and do you think I would still get the improvement I'm looking for in keeping my X1 instead of going for the BP26?
Thiel CS3.7 are I believe having some success here in France , I guess the fact that they are often demoed with Bryston amps/preamps in various shows is a reason by itself for a CS3.7 owner like me to want to look closer....and probably want to switch to Bryston . The impressions like the ones you quote from Cardas take certainly great part in our subconcious to always want to improve what we already have....I think this just nevers ends.
But since " the better is the enemy of the good " (quote translated from French) , it has played me tricks in the past.
Sometimes by wanting to improve just one part of our system we end up feeling it was maybe not worth the sacrifice....

Anyway , at this point, I guess everything makes a difference :the drive,DAC, cables, room etc...
Thanks again for your time in helping me make the right choices , it's really a pleasure (and a first as far as I'm concerned) experience.

Chris