6X4 or 4X4 tube? I have some nice unlabeled RCA 4X4's I think. An eBay seller had cases of them and was selling at a very good price. If you ever need any EL34's let me know. I bought a lot of them about 10 years ago, and they were "used" Svetlanas which were prior to the split...most of them tested as new, although I think they came from a guitar shop from guitarists who were told to change the tubes every show or some such.. For a while there I thought tubes were the stuff.....but now I am Phase Lineared and White Oaked pretty much through and through. I still like to listen to tubes, but the Phas Linears have spoiled me big time...
There is a nice Russian equivalent to the 6922....can't remember the designation right off, but they are VERY nice, but pretty darn expensive. If you ae rolling, I'd give them a try. The Russians have been making tubes for a long time, and some of the military stuff is excellent. 6P3S
http://www.ebay.com/itm/Matched-quad-6P ... 1e6943ea2a I think is a fabulous tube. Unbelievable. Or is it the 6NC3? They are here
http://www.ebay.com/itm/6P3S-E-6L6GC-58 ... 3cbfb0d718
Anyway, fun stuff to research and try. The Russians make some great sounding output tubes!