I've built and rebuilt a bunch of amps ... I have an original ST-35, an ST-70, a pair of MK III's, one of Shannon's ST-35's, an unrestored SCA-35, a Velleman K-4000, a Spark Audio 730D 300B, a homemade stereo 300B, a recently completed stereo 2A3 and just finished a stereo 13EM7/15EA7.
(You can see pictures of most of these on my website) http://mcnally.cc/amps.htm
Also - unrestored is a Heathkit AA-151 (6BQ5's) and worse, a Heathkit AA-100 that I bought a quad of JJ 7591's for, then realized the amp is a pile of crap. The amplifier circuit board is burned up, and the basic design isn't doing anything for me.
Anyway - I have a nice 17 x 12 x 2 chassis sitting around, and was thinking of mounting Shannon's ST-70 board below deck, and using the AA-100 transformers and the new 7591's and building a nice ST-70-type clone for my next project. Has anyone done this ? Any thoughts ?