another place to get JJ 12AT7: euro-e
Check out the gold pin version of the tube. I have tried their gold pin tubes and compared them with the standard 12Axx brethren and I felt like the gold pin version of the tubes was always sonically more complex. It is my understanding the gold pin JJ tubes are not JUST the same tube with gold pins, but the interior elements are different as well. Anyway, if you want to go with a new production tube, this is my suggestion.
If you have enough cash, do check out NOS 12AT7 tubes. It has been my ( and many, many other people's) experience that NOS tubes out-perform new production tubes.
And I agree with you about the initial situation... you will need a matching pair of whatever you get to ensure that your stereo image is accurate. That is probably the BEST reason to go with a new production tube, in that the re-seller can test and match a pair for you. Although a good re-seller of NOS tubes should be able to do that as well, but you may end up paying even more for the match. And two different brands will not only likely have a different gain structure, but will also, almost undoubtedly, have a different tonal voice to the signal. So do your best to get a matched pair, wether new production or a NOS set of tubes. Good luck!