Hi Carl,
Yes, the GK-1 uses just two tubes, 6ES8/CV5331, one for each channel.
The phono option (NOT standard; this is an additional $AUD210) is indeed IC-based. It uses active/passive split RIAA equalization, discrete power regulation, and a trick feedback network. It takes a MM output (typically 5mV) and amplifies it to about 1Vpp then passes it via the switching to the tube. So, yes, the phono also passes the signal through the tube.
I would NEVER pass up the opportunity of routing ALL signals through the tube! If you've got it, flaunt it!
BTW, about to pick up the prototype relay pcb for the remote Option 3, and once quickly assembled and tested, start the production run. Once complete, the GK-1 Option 3 (or is that GK-3??) will be in the market, behind schedule, but man, what an implementation. It's just marvellous; I'm delighted with it! And the Option 3 input/switching pcb is very, very good - a wonderful outcome which took a long time to get right.
Cheers,
Hugh