I am not going to use any new reissues, only interested in vintage tubes. I see no reason to just waist money on inferior sounding and less reliable tubes. But if you need 20 power tubes, yeah, you just might be forced into that. I only need a quad.
For bigger KT tubes, it’s extremely hard to find good vintage ones anymore. There are still some late make GE 6550s out there. EL34 (like your amp uses) and 6L6GC is much more feasible for sure. The British Mullards are warm (like your SED / Winged C, but better); I preferred Amperex / Holland EL34 for being more a bit more neutral while still sweet sounding. The East German RFT / Siemens are supposed to be quite good too. Electro Harmonix EL34 is a copy of this tube, at least superficially - but the old RFT build quality was much better (straight glass bottles, even!).
I’m quite fond of many of the Russian power tubes so it feels wrong to call the "inferior". But yes, the old power tubes were generally better. The old EL34 were beautifully built.
Also remember - part of VAC’s "secret sauce" is Kevin’s voicing expertise / craft, and it’s usually advisable to stick with tubes that sound at least similar to what it shipped with. What does VAC recommend for an Avatar these days? They were shipping Shuguang KT88 power tubes in 2000s (some with Penta Labs labeling), but Shuguang is long gone. I have a VAC 450S that originally shipped with those Shuguang KT88. They wore out before I got they got. Russian Gold Lion KT88 didn’t sound good in it, but fortunately Tung-Sol KT120 do :) Now that I think of it, might be worth tracking down some Shuguang KT88, sometime.