Thomas, it seems to me it might be appropriate for you to try a few different sets of tubes that are being made currently. Takatsuki, EML XLS 300B (which I use and love in my Audio Assemblage SET 300B, purchased on auction here on Audiogon for $750, and had caps and resistors upgraded).
Some might say I'm out of my mind using such expensive tubes in this amp, but I say they were absolutely worth it. A beautiful sounding amp. So, I would consider in lieu of spending tens of thousands, spend just hundreds (or in the case of the Takatsuki's, around $3000), and see if any of those would float your boat. I know of other SET 300B owners that are very happy with either the EML tubes or Takatsuki's.
Anyway, that's my suggestion. I don't know if you have tried any of these tubes, but if you don't try, you'll never know.
I hope you will be able to find what you are wanting, without spending such a large amount of cash.
Best regards,
Dan
Some might say I'm out of my mind using such expensive tubes in this amp, but I say they were absolutely worth it. A beautiful sounding amp. So, I would consider in lieu of spending tens of thousands, spend just hundreds (or in the case of the Takatsuki's, around $3000), and see if any of those would float your boat. I know of other SET 300B owners that are very happy with either the EML tubes or Takatsuki's.
Anyway, that's my suggestion. I don't know if you have tried any of these tubes, but if you don't try, you'll never know.
I hope you will be able to find what you are wanting, without spending such a large amount of cash.
Best regards,
Dan