I've dealt with all the above-mentioned. Kevin, though extremely busy, is dedicated to coming through for you, and can accomodate just about any need, but only especially if you have bought tube components from him. Bruce has some excellent, though somewhat limited, NOS alternatives (ask him about his Amperex stock). Although Andy has a knack for unjustly disparaging competitors' products while exaggerating his own, he does deal with some good NOS tubes. An often overlooked source with audio enthusiasts is Angela Instruments. Angela deals mainly with the guitar amp market, but the Siemens EL-34's I got are the best output tubes my amp ever enjoyed, at a lower cost than what most of the audio market charges. Very cordial, speedy service (301) 725-0451 or http://www.angela.com/
There are lots of tube dealers on the web, and most all of them are reputable. With NOS tubes, especially the rarest ones, availability fluctuates drastically. Often, the best thing to do is shop around.