I own C-J for both my amp and preamp, and although the models I have don't use the 6922 tube found in the '17, I will tell you that in my experience, C-J picks their tubes primarily for reliability of supply and for longevity, rather than strictly for sound. I've always been able to improve, IMHO, the sound of my amps by going to brands other than the ones C-J uses, but sometimes at the expense of shortened tube life (though not always). C-J is good about pre-testing their tubes, but you pay for it. You can find other reputable tube merchants who will test a wider variety of tubes and don't charge any more, often less. As for NOS, I shy away because of the cost, and because the few I've dabbled in have exhibited noise problems. However, I may not have gone far enough, both financially and in terms of seeking out a specialist dealer, to serve as an advisor here. There is little doubt that it is possible with many tube types that the best ever made are now NOS, and it's generally acknowledged that manufacturing quality was often superior during the tube's golden age, but finding a to-spec set of these without getting burned can be another matter, and the degree of sonic improvement is open to debate and will vary with the tube type in question. For the sound I've been able to achieve and am happy with, it's been simpler for me to just audition all of the currently manufactured brands and pick my favorite. At least you can count on fairly consistent results that way, and save some $ in the process. Just my $.02, I'm sure many others will come along and post about what you'll be missing if you don't investigate NOS, and probably give you specific recommendations - and they could be absolutely right, but ultimately, you'll have to decide for yourself whether or not to take the plunge. Good luck!