Tube vendors.

jim m is very good with testing and supplying modern power tubes - he is not really an active chaser of old rare small signal tubes - he may have some occasionally but he is not like andy baumann or brent jessee who will vigorously chase estate sales and do laborious sorting and testing of old rare tube collectors that have passed or are emptying their stocks due to age

kevin started travelling all over the world chasing good old stock tubes he has quite a stash he is selling down over time

i don’t know as much about the tube store but they also seem to have some old stock tubes as well, and they also seem to have a rigorous test regimen

for good, now increasingly rare small signal tubes and rectifiers i would say andy @ vts, brent jessee and k deal are best, they test and they still have decent supply and variety - of course you will pay through the nose for the rare good stuff, for some tube types the cost is still fairly reasonable

the viva shop in mass is good, they ship quickly, communicate very well (sometimes a problem with andy at vts as he is older and essentially a one man show, as is jim m), viva is also very responsive when issues arise with tubes they sell

that said, i don’t believe viva does extra testing in house or burn in on their tubes, which can be quite important and valuable with some tubes for some amps... for new stock tubes i believe viva relies on the factory testing and matching, which for some makes and tubes may not be so great