Steve, here are some of the sites I've looked at over the years:
Transcendent Sound--tube gear. I don't have any of the kits, although I've wanted to try some. I do have a book by Bruce Rozenblit in which he shares his philosophy and knowledge about tube based designs. Schematics for projects are included.
Bottlehead--more tube gear. I bought a preamp kit years ago and it's still under construction. Very easy to follow and build. There is a headphone kit in there.
Aspen Amplifiers--here's some solid state stuff. These are from Australia and more info can be found
here at the Audiocircle forum.
Hopefully some of these will help!
