You need to go to http://www.thegearpage.net/board/
and do a search on tube amp kits. Many folks there have built kits, and many boutique amp builders post there. You can also find your way to other more specific amp building sites like www.ax84.com.
I'm planning on doing my first kit in the next six months or so, and I have been reading up on the subject of circuit design in the meantime.
Hope you give the Gear Page a try. Great folks over there and drama is kept to a minimum. I'm registered there under the same user name. Good luck in your endeavor!