For whatever it might be worth to those here...
I've A/B'd most of the current production preamp tubes in my Boogie amps, in each of the tube positions. I also found the JJ's to be rather disappointing. A bit dark, dull, flat, and lower in overdrive. Might be great in an amp that was excessively bright by nature, with a lack of clean headroom, but not ideal, IMHO, for any Boogie. Usually results in a duller, more rounded, sound with less apparent overdrive.
Many Boogies, as most of you may know, were designed around Chinese preamp tubes which are on the brighter side and have a good ammount of overdrive potential. What this translates to is that these circuits work closest to how intended when designed, when used with a tube with similar characteristics. My favorite tube has these characteristics, is very 3D and alive sounding, but is very prone to microphonics in high gain slots. About 80% go after about a month. Bummer. However, I prescreened some batches of these and have a stash. The closest thing that I've heard to these is actually the Sovtek EH's that Mesa is currently using. These aren't quite as gorgeous sounding, IMHO, as my fav, but are closest than anything else I've heard that isn't NOS and are plenty durable. I think they're actually pretty great little tubes!
In terms of power tubes, I haven't done AS MUCH A/Bing, but I will comment that, for Boogies, the Chinese 6L6's do, IMHO, sound pretty good and do not at all deserve the bad rap that a lot of people give them. Reliability isn't as good as some, but I've had good luck. The tone works very well with the voicing of Boogie amps. Probably because of the similarities to the Sylvanias used in the original designs, as pointed out earlier in this thread. The best EL-34's that I've heard have been Svetlana's.
Anybody else have some favs?