According to Bob Carver, there should not be a significant difference in sound between the two amps except for the extra headroom of the BBs. I have heard that the KT120s on the BBs may sound a little sweeter up top than the stock KT88s in the Cherry 180. But you got so much choice in KT88s, you could probably get the sound you're looking for by tube rolling. You can't with the KT120, which is only made by one manufacturer. Based on what I've heard from the latest Bryston amps in different systems (but not in my own), I can almost guarantee you that Bob's amps will have better sound staging/imaging, more harmonically correct and less fatiguing sound than the Bryston. Bryston will probably have tighter bass. That's my edumacated guess based on my experience. I think Thiels relatively lean sound will benefit from a good tube amp.