Have you guys ever tried the Russian equivalent of the ecc83/12ax7? Or even their 6V6 or EL84 tubes? They can handle much higher plate voltages and sound incredible. I use them in my builds, the 12ax7 is easier to wire up too as pin 4 and 5 are heaters, and pin 9 is used on an internal shield.
The other good thing is they are cheap too, I paid £12 for 4 12ax7s and two EL84's.