My all time favorite 12AX7 tube is Telefunken smooth plate. For 6922, I have had good luck with Siemens. I think you need to try different brands in your own gear to decide what suits you the best. I would choose a good tube seller. I have had excellent results buying new and used tubes from Brent Jesse Recording. He is very helpful by telephone and has a very user friendly website.
Time for new tubes.. which ones?
My TAD-150 preamp which has only 2 tubes stays on all the time, so every year I have to replace the tubes. This is my first time replacing them. Does anyone have an opinion as to what tube to use, or should I just use the same replacement ones from TAD? I would like to improve the sound if possible with new tubes. Thanks