Just FYI/FWIW here are some comparisons between my amp and what we know about the Sarah 300B.
My amp weighs 40 lbs, and most of that is the transformers. They are pretty bad a$$, and probably why the bass is so tight and well defined. I don't know how much Sarah is going to weigh, but for comparison the SE34I.6 is 18 LBS.
Both amps have AC circuits for the heaters. Mine has a screw to adjust to minimize the hum. Hum is kinda a trigger for me and with my 95 dB speakers there is some. I can hear it at the speakers, not so much from my seat (but I know its there...).
Sarah has a tube rectifier, which would be my preference. My amp is SS rectified, and has a (presumably) can'o caps bigger and taller than a 300B tube for power supply reservoir. It also has a 10 second soft start circuit, where as I believe Sarah is choke regulated.
Probably the biggest different (at least topologically) is the input. We all know about Sarah's "zrock inspired" input circuit that uses the Decware standard 9 pin input tubes. The thing that really got me interested in the Space-tech amp is that it has a balanced input circuit with 6S[N|L]7 input tubes. The balanced input drives the 300B tubes which are single ended. For me, the 'L7 had too much gain so I've been using pairs of single triode equivalents of the 6SN7: 6J5GTs, VT37 and my favorite GEC L63.
Finally the cosmetics. The Space-tech amp is gold finish aluminum, and is not really my style. I much prefer the Decware look, but what are you going to do?

In other news some "friends" on another site convinced me to get the Takatsuki 300B tubes so more on that later...