Got the head (silverface Bassman 100 head) a few days ago, with intentions of replacing the preamp and driver tubes just because I'd never had a chance to do so before (the only amp I've ever owned was a GK400RB-III, which I have and still love). I just ordered from the Tube Store 2 GE 5751 preamp tubes. I have a USA 7025 in one of the slots right now, and the other is a no-name 12AX7. I plan on mixing and matching until I find a combination I like. If one of the GEs doesn't get used, I'll hold onto it. I also got a Mullard 12AT7 for the driver slot, where there is a USA 12AT7 right now. Again, it'll be trying things to see which I like better, and I'll end up with a few extras probably. The amp has 4 fairly new Ruby 6L6GC STRs in the power section. I've decided to keep these in for a while, as I might turn this amp into a tinker amp this summer vacation and do something evil with the power section.