Paul, I think Jadis supplies KT88 tubes these days in the Orchestra and DA lines. Pierre Gabriel does take pictures with a lot of tubes, however. And, it shows the flexibility of the amplifiers.
I believe Jadis was using KT88 in the mid - late 90s, but a few infamous bad batches of the Teslovak (now JJ) tubes caused them to try and keep the more bulletproof Ei KT90. They then returned to the KT88 as they feel it to have better sonics. This was before Pierre was the distributor in North America. When I bought my JOR, Frank Garbie was the distributor.
I was speaking with Pierre last week. I was kind of surprised to hear that, like me, he likes the EL34 sound best. The issue of power with this tube is a lot less than one would expect. I guess the transformers may help here. The drawback is what you lose in the lower end, and it cannot be denied.
The newly released JJ KT77 really produces the kind of bottom end I demand. And, while its mids are not up to the incredible level of the JJ E34L tubes, it betters the JJ KT88. I see it as the best overall compromise in my DA60. In the DA30, I'm running the E34L tubes, even though it's an older unit, and should be only using the 6550, KT88, or KT90. I'm kind of trying to run them, then see how they measure, just to see if the fears of cooking that tube too quickly are actually true.
Again, I'm not a fan of Russian tubes. The Sovteks have a irritating sound, and the EH go way overboard on the politeness thing, which sounds solid state to me. The JJs have a house sound of vividness and brilliance that works best for me. Still, they will not be everyone's flavor. I ran the Ei KT90 in my JOR until I went to the JJ E34L, and while I lost bass and a little power, the gain in beauty and wow factor made me a Jadis devotee for life.
Interestingly enough, I am finding the current production of Chinese tubes to be fantastic. I would have never believed it, but they actually are surpassing a lot of the NOS tubes I have on hand. No one would have ever been able to convince me of that I can assure you. Even the older ones err on the side of richness, so I prefer them to the Russian tubes. The new Chinese tubes seem to have changed a lot of their construction, and have really upped the performance. They're no longer junk. Others I trust seem to feel this way about the KT88 the Chinese are making now, and VAC even supplies them as OEM, which is saying something if you know anything about the kind of person Kevin Hayes is.
Rolling the 12AX7 means trying different versions and manufacturers. Ei that Jadis supplies are about as good as most modern manufacture. Though I hear great things about the JJ 12AX7 (ECC83) and their new ECC803, though the latter is a higher gain tube. Lots of people like NOS 12AX7, the Telefunken Smooth Plate being considered the Gold Standard, and commanding the most money, even if I have found superior tubes in my experience.
Rolling the 12AU7 if you get a DA30, DA50S, DA60, or DA88S would follow the same pattern.