I put in a set of high gain JJs and was underwhelmed. Doug's has a set that includes 3 or 4 tube types so you can tube-roll. A lot of people are recommending Mullard box-plates (if you can afford it) or Tung-Sol in V1.
Mesa tubes now come from the same factory as JJ (Czech). Avoid the SPAX7, it has really low gain in my experience.
There are only 2 factories left, Czech and China. Lots of NOS ones out there, though.
Do you want lots of clean headroom, heavy clip, or something in between? Do you want bright or dark?