Well, personally I'm finding that vintage Amperex (Orange label PQ) 6922s work very, very well in Valhalla 2. Currently examining Amperex 7308s, both white label JAN and orange label PQs compared to those Amperex 6922s, but it's too early to tell yet, as I am still running in the white label tubes. They all sound very good, better than the stock JJs, but somewhat different from one another. I haven't decided on my favorite yet. You can see some of my tube rolling comments in the Valhala 2 review thread. I also have some Ediswan 6922s in my CJ LP70S power amp that I need to roll in, as well, and see how those perform.