nkonor,
I rolled a LOT of tubes when I got my Steelhead (~ 2005). I ultimately had no difficulty settling on Siemens CCa's and Bendix/Mu 6900's. Siemens was definitely more revealing than Telefunken. The 6900's were much cleaner than any other tubes I tried in that position. Still have those tubes in there, totally satisfied (don't get to listen nearly as much as I'd like).
Now for the bad news. The CCa's are pretty available, but expect to pay $300-$400 for a real NOS pair. The 6900's are even worse - almost unobtainable, my guess is $250-$400 each if you can find them.
Richard