Last year I built a bone stock ST70 kit from dynakits.com I also bought a VTA board along with triode kit to convert it to after getting a baseline on the stock amplifier.
I own a lot of highly regarded tube amplifiers, and with the modern resistors and caps and decent tubes (RCA 7199 & JJ E34L), the stock amplifier is so captivating, I've never felt the needs to implement the upgrades I've already paid for.
For what it's worth, I'd recommend rebuilding the driver board with modern parts and see how you feel at that point.
I own a lot of highly regarded tube amplifiers, and with the modern resistors and caps and decent tubes (RCA 7199 & JJ E34L), the stock amplifier is so captivating, I've never felt the needs to implement the upgrades I've already paid for.
For what it's worth, I'd recommend rebuilding the driver board with modern parts and see how you feel at that point.