Well said @bob540
The art of the hobby on the tube side of things is to properly match the system. Obvious I know but there is alot of terrific sounding gear that doesn't require an esoteric tube set to sound exceptional. For instance, Audio Note ships with a nice blend of new production tubes with the occasional NOS tube here or there. Shindo utilizes non traditional tubes that can be quite inexpensive. Leben sounds amazing with all new production tubes and with rare exceptions, rolling in NOS doesn't necessarily mean better....just a little different. These manufacturers voice their gear that way. Audio Research uses reasonably priced new production tubes and they achieve terrific results and besides, other than some of the unobtainable Reflektors, there are no other makes in 6h30's or KT150's.
For most of us in the hobby, NOS tubes can emphasize certain sonic traits that we either enjoy being overemphasized or more likely, certain NOS tubes help us OVERCOME the shortcomings of the gear we have chosen. Be it vintage, new production or gear that comes equipped with questionable quality new production tube sets, there are some wonderful tubes being made today for audio purposes.
My next comment applies to me and to many others I am sure. I buy a piece of gear and let it break in, and I love it. Then I decide if its good as is, imagine how good it could/would be if I rolled in X, Y or Z NOS tubes. SOME modern gear can benefit from NOS tubes but not always. MOST vintage gear benefits from NOS tubes but not always. Listen to an old Scott 222c full of NOS Teles and an old Mullard rectifier and you wonder why we even bother to chase the grail when that 60 year old integrated sounds that good. I've connected mine to $20k+ speakers and a $10k + dac and I just shake my head. Its the cocktail of the old iron, well done circuits and the best of tube manufacturing from a time when tubes were mission critical. With that said, there is some amazing new gear being manufactured today that show just how far the art has evolved.