SofTone TXs have been discussed on various forums before. They have been used by a couple DIYers who seemed to quite like them.
From memory, they seem pretty decent, though hit saturation (causing associated bass limitations) quite early; @ ~6W output I think. They would be pretty good for 45s and 2A3s... even 300Bs at lowish plate voltage / dissipation.
I seem to recall some positive comments re an amp using these in an active set-up... running on the mids I think?..
Anyhow, these guys seem pretty legit, with lots of test results on their site - I can't offer an endorsement tho.
Best of fortune with your search, Raymond.