There are lots of schematics around the Web for GM70 SET amps. I think, given my speakers (KCS Fostex F200A; reasonably but not highly efficient) that GM70 SET would work very nicely in my room.

Does anyone know of an independent amp builder who'd be a good choice to build a custom pair of GM70 monoblocks? I know about SAC Thailand, but I'd prefer to deal with someone in the US.
Yes, I'm familiar. Not really to my taste, aesthetically. Also, was hoping to spend less than $13k.
Two outstanding builders that have stellar reputations, great personalities and are knowledgable as heck: Jim Dowdy (North Carolina) and Jeffrey Jackson (Tennessee). Both have sites. Jeffrey has an excellent blog and go to You Tube to see (hear) Dowdy's GM70.

You can also go to the Oswald Mill site and then proceed to the Tastings at the old mill in Pennsylvania. There you can read up on both builders and see some of their creations (including GM70 amps).
Oops, forgot to add that Oswald Mill has a new GM 70 amplifier as well. Probably will not, however, fit within your stated budget whereas the other custom builders will be pretty close to what you desire to spend. In any event, you can work with them around your budget until you get what you want.