The Don Sachs and Lynn Varley Revelation (Raven) preamp and Blackbird 300B amps seem extremely interesting. I've followed their 300B thread here on Audiogon (where Ralph from Atmosphere has added a ton), and it is a master class in tube amp and preamp design and theory. I've learned a ton; it's a long detailed read.....and above my level of knowledge, but I've learned a lot.
I'd love to read your experiences