You can find the KGSS schematic on www.headwize.com under the projects link. It too is balanced like the 727 but the reason why I like SE is the simplicity and fewer parts. I would much rather have a SE 1. drive stage and then use a transformer as a phase splitter but I'm a SET guy at heart and transistors are icky...
It can handle 30v because there is an internal switch to bypass the volume control and run the amp directly from a preamp.
The non-NFB isn't really an issue for me as Stax has made some of the best solid state amps ever designed. They were speaker designs but they are still unmatched. NFB is good to get better numbers but if the circuit behaves well without it I see no reason to poison the sound quality with NFB.
Just go with tubes and get it over with. I'm toying with a few push-pull SET ideas and how they could be converted over to Stax duty. That is really the ultimate Stax amp.