YOu can go as wild as you want with NOS 6922s, all of which are an improvement. I've used Amperex 6922 PQs (nice and not too expensive), Siemens 6922s, Tungsram and Siemens CCas (very nice and due to long life, they can even be used if they are well matched). Haven't been too wild about differences in the 6V6s (used Brimar, GE and Sovtek).
