I would look for Type 80, Type 280 or 380, 5U4, 5V4, 5Y3 or 5AR4 rectifiers, input tubes that are 6922, 7308, 6DJ8 or 7DJ7, and EL84 power tubes. Different brands will sound differently combined with the others, I've been surprised enough to not pre-judge too much.

Of course in the last year or so I've come to think that the SV83 type of power tube and the Russian 6N1P and 6N5P input tubes to be the best for my system and tastes. Experimentation will help you find what works best for you and your system.

Holy grail. That would be tubes like metal base EL34's, any WE's, pre 60's 12AX/U7's with maybe square or goal post or foil or disc getters. Some TFK's ..............

Thanks for the help - Yes - most are 'used' but there are some NOS that I'll search and try.