Russian Tubes or Old "American" Tubes (built where ever)?

You should check out the GE 6DJ8 . I like these tubes and they will not cost you an arm and a leg. I use all GE preamp  tubes,12ax7,12at7,12au7,etc.  I like the ones from the 50's and 60's the best!

Put the Russian's in and see what you think. It's system synergy that we all search for with all of our equipment/part choices.
What works for you may not be good for someone else.
Consider tubes in audio like spices in cooking. Different tubes will give you a different "flavor".
Is that "flavor" good, better, or bad? That is a subjective choice.
I would suggest, that as your budget allows, buy a replacement set of tubes that you are interested in trying. See if you like them. If so, great. If not you can always sell them and recover most of your original purchase price.
I have a very extensive collection of tubes and can tell you that even within the same family I.E. GE, RCA, ETC, there are many differences in sound.
Depending on what flavor you are searching for will determine your choice.
Most of all, have fun with it and trust YOUR ears.

P.S.  I forgot to mention to do a search for "Joe's Tube Lore". 
He has done a rather extensive shootout of several different tube families. 
His results are a good read and a good starting point. 
Remember, your results will/may vary from his. But Hey, isn't that what makes this hobby fun?

Many NOS tubes are very good, but the can get pretty pricey. At least you are only looking for a pair, which helps a lot. The NOS market can be scary and dangerous if you don't know what you are doing. Pricey, but some shady re-sellers out there.

For new tubes, I have found the Psvane tubes to offer very good quality at reasonable prices. Of course, as always, YMMV.

Thanks for the responses. I’d love to have more suggestions and reputable sources for tubes and thoughts about the quality of the Russian/modern tubes vs NOS tubes. I’ve had the pre for quite awhile (and I still have a couple of others including SS CJ) and have generally used older tubes.

Let me clarify: My plan is to buy some tubes in addition to the spare ones I have. I was hoping to get some feedback from folks about the tubes that they have used (particularly if they have used them in the CJ) so that I could cut my selection down and save money in my process of evaluating a few sets of tubes. The pre-amp actually takes 4 tubes (not 2) so depending upon the tubes selected it can get pricey. Particularly if I follow the "test a bunch of tubes in your system and pick the one that sounds the best to you" approach.

 General observation: I think we would all agree that a particular brand and/or set of tubes would sound best in my system and in my room, but I don’t have the time and/or money to try every combination to achieve that goal (I’d be potentially more cost efficient by going out and spending the money on a different pre-amp). If our advice becomes “trust your ears, in your room, with your equipment” although it is an accurate assessment we then lose the benefit of the community and reviews and comments become irrelevant. That’s part of what a forum is designed to do: share experience and wisdom across audiophiles.

Personal experience: I know I can sell the tubes used. I always intend to sell my old equipment, but I have observed that I tend to keep it (with the exception of the really pricey stuff and then I price it to sell before my wife goes insane).

 So again – thanks for the advice, more is welcome; after 45 years of tinkering I still have lots to learn.

PS
What's YMMV?
Joe's even more anal than I am and must be single and rich (thanks for the reference)!