@noromance - I'm using a Jensen input transformer for the balanced inputs. The driver stage is coupled to the 300Bs using a c-core interstage transformer. Then another c-core transformer for the outputs.
The 300Bs each have a Tentlabs filament supply (voltage controlled current source). The driver tube (6SH7) has a Pete Millet regulated heater supply. I'm also using a Neurochrome 21st century Maida regulator.
@lucky_doggg7 - yeah the WE tubes don't come cheap. But right out of the box, they were very clearly superior to the Linlai tubes I started with (mostly because I didn't want to risk damaging an extensive tube when I was first checking out the amps).
I'm using a DIY preamp which I'm pretty happy with. This is my second DIY preamp build. You can see details on my virtual system page.
At this point, it's unlikely I'll buy another commercial product. I am really enjoying the whole process of building my own. So far, I have primarily been using subassemblies designed by others, but I'm starting to experiment with my own ground-up designs as well.