JJ preamps are worse for the mud than the power tubes, but I don't really like either of them for tone.
JAN/Philips tubes are some of the highest quality tubes ever made, period. This goes exactly to show what I meant about quality not being very (if at all) related to price with NOS tubes. As to tone, that's personal preference. Individual types vary, but like most of the makers there is an overall 'family sound' - I would say they're generally clear-sounding and can seem a bit cold, but they also have very good depth and detail, if that's your taste. The power tubes are getting rarer now, especially the 7581As which are basically the same as the Philips/Sylvania Mesa STR415s but with an even more ruggedised military-spec construction. I put a pair of these in my DC-5 and it got so much more bandwidth and punch you would think it was a 100-watter. In fact, it increased the power from a measured 55W with the stock tubes to 63W, which is a huge increase just from changing tubes of the same basic type. From a technical point of view I would guess that they all have a very hard vacuum compared to a lot of the other makes, which would explain the sound and power, and also the very good reliability and life expectancy.
For what it's worth if I was a major label artist I would use the stock tubes in my touring amps too. On that kind of gig it really wouldn't be the highest priority - in a little club venue where both you and the audience *are* hearing the amp I would go with NOS every time, but mic'ed through a huge PA, hearing it through the stage monitors or IEMs, with the amp getting moved around every night by roadies, let alone airline cargo handlers, keeping spares, replaceability (of the amp as well as the tubes) if something goes wrong... stock all the way, there's just no point in getting too fussy about it.