Erfranke,
Thank you for bringing the Tube Audio Lab site to my attention. It appears that the various designs are based heavily on old topologies and clones of specific designs, like the Western Electric amps.
My only concern would be, the extent to which the designer/builder actually listens critically and has made design and parts choices based on such auditions. There appears to be a lot of mix and match alternatives when it comes to the specific parts. I know that part choice is EXTREMELY important, and there is no such thing as a "best" or "better" part--it depends on application and personal taste.
I've heard amps where the "upgrade" consisted of replacement of cheap capacitors and resistors with much more expensive, and supposedly better, parts, such as Blackgate capacitors and Vishay resistors. The result of using price/popularity as the guide, instead of auditioning the results, were horrible; the designer chose those "cheap" parts for a reason.
If you go this route, it would pay to have a long discussion with the designer/builder about what he actually knows about specific choices. He does offer a terrific range of parts (when used correctly), and there is potential to make fantastic gear with the likes of Hashimoto or Audionote transformers, etc. But, there is also the potential to make extremely expensive disappointment too.
