I ask this question with complete sincerity. What is the fascination with vintage tubes? I can't think of much else where people put such a premium of things built decades ago. Nothing technological that I can think of. Are there some materials that are no longer available to modern tube manufacturers? Is there a secret process that has been Lost? Surely, we must be able to manufacture tubes today with the same care and attention to detail. In virtually all fields, the passing of time leads to improvements in the manufacturing process. So why are audio tubes, apparently, an exception to this rule.
Would you buy a tube amp if you were unable to use vintage tubes in it ?
Not available or too expensive.
Hmm.., I don't think I have a definitive answer for myself, but I would do my best to avoid such amps. There is no substitute for great tubes, I guess, especially if you value sophisticated sound.