Would you buy a tube amp if you were unable to use vintage tubes in it ?

@inna Sorry to be so late to this. If I may add a humorous aside?

Keep anything long enough and by default it will become "vintage". 

IMHO, much like the halo around "Cuban cigars", I think that "NOS" tubes are somewhat overrated. "Old" doesn't necessarily translate to "better". Yes they were "made differently" back when, but modern materials and manufacturing methods are unnecessarily demonized. Let your ears be the judge.

Happy listening.

@musicfan2349- I was pretty picky about my cigars too and probably had more depth in those at one point than in NOS tubes (which have all kinds of nuances re where manufactured, when, getter, and other internals and I only have knowledge of the tubes I've used).

The benchmark for me was a spicy smoke that wasn't harsh- I was able to experience everything from pre-Embargo to Davidoff cubans, and my go-to was a good Monte #2 but they were variable (I guess b/c they are organic, but I don't know if wine connoisseurs find bottle to bottle variations; that was certainly true of cigar batches, leaving aside "vintage"). Alas, I had to give up smoking many years ago for health reasons so have no clue what that market is like these days.  

My preamp is Conrad-Johnson's top model the ART88.  It came brand new from the factory with four Phillips NOS ECC88's.  I read in a HiFI+ review that you could replace the "made for TVs" NOS tubes with EH6922 Golds for a nice increase in sound quality.  Okay, so ordered a set.  Yes the change was immediate. Jeff, the designer at C-J said he thought the EH's might turn noisy but no harm.  After a few months, there was no noise from the EH's but thought I'd put the NOS tubes back in and see how they sounded.  What I discovered was a definite preference for the original NOS tubes.  The sound was better; richer in the mids and just as detailed.  Turns out, I was fooled by a bit of extra gain from the new production tubes.  Slightly louder, of course, sounded better at first.

Guess the process is to listen and see what you prefer.  The HiFi + review has  different gear so came to a another conclusion.

My tube preamp is a Linear Tube Audio MZ2. Maybe tube rolling changes the sound, but I prefer a different tool: the five-band parametric equalizer in the RME ADI FS2 DAC. Sometimes I run it flat, and sometimes I run it with a boost in the lower midtones (250 - 500 HZ). The difference in sound is apparent. And the DAC should last longer than almost any preamp tube.

Well, contrary to what others have posted, I understand that many phono stage manufacturers ship their units with crappy stock tubes. The reason? They know that tube sound and quality is relatively subjective, that people pay top $ for some tubes from the 1950s, that tube rolling exists and that therefore the user is going to immediately put his or her own tubes in upon installation. 

As I did.