I recently upgraded my amplifier's input tubes from Sovtek 6922's to EH 6922's. They are very similar, with better bass response coming from the EH tubes. You might give these some consideration, at $20 each new with gold pins. Don't go down the NOS road unless you've got so much money that you've forgotten what One's and Five's look like, and you'd better have reliable sources, because (IMHO) many of the NOS tubes circulating through cyberspace right now are actually OOS tubes (Old Old Stock) or just plain OJ (Old Junk).
Cheers and Good Luck