I'd stay with the RCAs. They're cheap and plentiful. You don't worry about them going bad and how you would replace them. If you want to experiment try the military 6080 which is available under RCA, GE or Sylvania labels. I have no idea about the sonics -- I'm just looking at what I would do from a practical viewpoint.
Telefunken 6AS7
Anyone have any listening experience with these tubes? I am currently running RCA's in my OTL amp and was wondering if changing to these are going to give a wow factor, or just a different sound. They a very expensive at $700.00 - $800.00 for a quad of NOS. Or are they just pricy because they are a collector's item (which I am not interested in)?