JJ's are perfectly fine tubes. That being said, in the V1 position of any tube amp, the first preamp tube is going to effect the sound the most. So trying different preamp tubes is a cheap way of getting a very slight change in frequency response. With that in mind, different tubes in your preamp take more wear than others, most notable, would be the reverb tubes, in which case, you could argue having any newer tested / otherwise decent tube in there would be a good idea, but they dont effect the tone AT ALL, and reverb is after all, just noise, so JJ tubes are great tubes for reverb. Why put an expensive tube in a socket that isn't going to have any effect on tone? As for power tubes, according to Mac at Two Rock, Keith at Redplate, and Dan at FYD, the matched power tube sets do make a difference - but that doesn't necessarily lead them to rush at NOS tubes - ever. TAD, 6L6 GC STR's, there are plenty of great power tubes out there. Currently digging the STR's, but I would say its best to check with the person who made your amp, or in your case the guy modding your circuit, maybe they will have a good idea of what they like.
With 6v6's I've had great luck with JJ Apex brand matched pairs - they sound great, and seem to last a really long time. Not so much tonal difference with premium tubes in the 6v6, had access to Tube Depot's entire inventory for a long time in Memphis, and really, the JJ's were great when bench tested side by side with basically everything they offer in a premium price point. My tech worked there and we were testing options with my 2 touring deluxe reverbs. Cost me a decent penny in labor - so happy to share that one.
Quick note on Gold pin tubes: I live on the Coast of California, and corrosion is a bitch. The Gold Pin tubes can be less trouble than pulling and scrubbing the pins on your tubes 1-2 times a year, but really, if you live on the ocean, you should be doing that to all your tubes anyway.