OK Tom, bear in mind that a lot of this is subject a lot of personal biases. I love the Krell on Thiels. IMHO they are not nearly as bright and lean as some make them out to be. While the McCormacks have nice tight bass and smooth liquid highs, I think they can be some what forward and shouty, not something that would compliment the Thiels. I haven't heard the Theta's. The Brystons are nice, I particularly like the 3BST. The Brystons are probably some where between what you have now and the better amps on your list. How ever there has been some talk here on Audiogon with regard to their inability to handle low impedance loads. Considering your 3.6's drop to 2.5 Ohms, I'd be more than a little cautious. I find the Classe' a bit soft in the bass and a bit chalky on top. These critisims should not be taken out of context, I really do mean a bit. Rumor has it that the 200 Watt and above models are superior to the lower powered versions. The Classe' is probably between the Bryston and the next level, but I wouldn't argue if others placed them differently. The Classe' is a sound choice for the Thiels. The Pass X series might be the best amps I've ever heard. I love the lack of electronic flavor/haze that dwells in so much solid state gear and they are a lot cleaner and more dynamic than the Aleph predecesors. They should work beautifully with the Thiels. Unfortunatley your budget may prohibit the power levels your accustomed to. From your short list I would consider in order: Pass, Krell and Classe'. If any others come up for consideration I'd be happy to share my arrogant, pompous point of view. While I think that amps may be more important with Thiels than most speakers, try not to forget how the amps will work in the complete system, now and in the future. Good luck
