Albert's point is well taken and something I mentioned earlier. If the circuit is demanding, like driving real hard or whatever, then there probably are tubes that work better than other. Maybe NOS, maybe not. I have also had good results with new JJ and EH small signal tubes. (I have a pair of the new ECC99 on the way, heard several good reports on these.) I'm using some NOS Tesla right now that I find very special and they only cost $40 a pair. No, I won't tell you which they are cuz I don't want the price to jump. ;-) In my amp I have found that the new production EH EL34s are better than some very high dollar NOS EL34s that came with the amp when I bought it. These were supposedly the best EL 34s ever made. I can't remember exactly what they are and I'm not at home right now to check.
Not to stray off topic too much but I have moved away from such equipment because I have found other designs that work better without the need to drive the tubes hard. I've also not found in my humble experiences a design using the 6922 that I like. And I've tried the PQ white labels and a few others. I'm not slamming any make or model, just hoping to help explain why some may find NOS necessary and others can find great performance with some current production tubes.
Not to stray off topic too much but I have moved away from such equipment because I have found other designs that work better without the need to drive the tubes hard. I've also not found in my humble experiences a design using the 6922 that I like. And I've tried the PQ white labels and a few others. I'm not slamming any make or model, just hoping to help explain why some may find NOS necessary and others can find great performance with some current production tubes.