groove tubes are an overpriced testing service, though their EL34m is a really good sounding tube made exclusively for them in china, but they have piss poor longevity.... their USA made 6L6GE is killer and lasts forever, but is SO expensive compared to a JJ 6L6 its not worth it
in 12ax7s I like new sensor's tung dol reissue.... very gainy, rich sounding tube, but they have a high failure rate so go through a dealer with excellent testing... otherwise JJ pres are solidly made and sound good enough if you are on a udget. A lot depends on the circuit and how well trained your ear becomes. I seldom care about tube brand for live purposes, just recording. The whole thing can be diminishing returns, especially if you are a pedals and master volume modern player. So much of the difference between old and new pres is FEEL. If you don't play the amp then it won't matter a ton. The old stuff tends to sound a bit better if you listen critically and lasts a really long time. Otherwise its a question of optimizing the response of the whole amp to respond to your playing the way your personalized guitars do so the whole thing becomes a single instrument geared to the way you play. I am way down that rabbit hole having never been a huge effects head and having a very old-school approach to actually playing guitar. It suits me, but it won't suit everyone.
That said, while 3 of my amps have nice vintage pres throughout right now, one has the stock Chinese tubes and no one thinks it sounds bad and it feels fine to me.
my overall answer is that the most reliable current production pres are JJs across the board. They are a little dark sounding compared to old stuff and even most current production tubes but this also means they don't harsh out at extreme treble settings and will smooth out pedals like a DS1. If you are going to use effects heavily through a modern amp design with a master volume and lots of features, leave all your guitar controls full up, and generate any non-pedal drive from the preamp? JJ is probably a great way to go unless you are looking for lots of treble and more distortion on tap from the gain control. You gotta consider how you play your amp and if reliability or response is more important, or if you want to go nuts on a quest for both. Its expensive these days, most of my old tubes were pulled from old gear abck when people weren't as hip to all this stuff. I got into it because it suited me, then the market caught up wth my tastes. YMMV though
