[Arran]

There are what we in the radio hobby call "Audiophools" (audiophiles) that will swear up and down that one brand of tube is better then another, or that NOS American, British, or European makes are better then the Russian or Chinese types for sound. What it really boils down to is having two tubes as a matched pair, same type, same emission, same brand, with the same suffix like is there is an "A" after the "G" or "GT" in fact having both of the same brand may not be that important so much as the emission of each tube being within a certain range of the other. In the case of Philco most of their tubes were either made by National Union or Sylvania, Sylvania also made tubes for Zenith, so a Zenith, A Philco, and a Sylvania marked tube could very likely be from the same source. There are some Audiophools that get obsessed with production runs, date codes, and even the colour of the plate inside, in truth I do not know of any evidence other then anecdotal that supports this. I think the condition of the components in the surrounding circuitry will have more of an impact, leaky condensers or resistors that have drifted in value can throw tube biases way off. Sometimes it's a matter of the speaker, it's size, condition, and quality, hook up a decent six inch speaker in place of a four incher on an AC/DC set and you will be pleasantly surprised.
Used tubes are fine, if they test good, in fact used tubes that are known to be good have less of a chance of failure then a NOS tube since they are already broken in. As for stocking replacements, you can do so but there really is no hurry unless there is a catastrophic failure like a condenser shorting out, with the amount of use that a restored old radio gets it will take a long time to wear the tubes out. If there are a few tubes that are a little weak or borderline on emission then it might make some sense to replace them if only to boost performance.
Best Regards
Arran