What version is your Uberschall? Do you know how to bias a set of tubes? Are you talking power tubes or preamp tubes?
Gotta know what yer doing before you get in there, the caps can send you across the room if you're not sure about what you're doing (read: electrical shock).
I personally like JJ E34Ls in my Rev 2. They have a nice midrange, they're punch with a deep low end, and the highs aren't as harsh as SED EL34s. I also prefer all Chinese 9th B 12AX7s in the preamp section, although some people like to mix and match tubes there. What are you looking for in the amp?
I'd say Chinese 12ax7s (I had GT 12AX7-C in mine) for preamp and Svetlana C EL34 for poweramp. JJs mentioned before are also good, but you need to be careful and buy some kind of sorted ones.