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)?
I wonder if Telefunken actually manufactured a 6AS7? Many tubes, even top quality ones were sold as re-branded.

Example? The best 12AX7 tubes from Radio Shack were Telefunken (yes, a long time ago). Many EL34 marked as Dynaco, RCA, GE, Amperex or other names were manufactured by Mullard.

If it turns out the rave over Telefunken 6AS7 turns out to be (another brand here) chances are they can be bought for a fraction the cost.

Maybe Ralph at Atma-Sphere will see this and respond, 6AS7 is a tube he knows a lot about.
I'm thinking the same way as Albertporter. I can't ever remember hearing of them actually making one. Atma-Sphere may know. Also whether the tube says Made in Germany on it might give you a better idea.
Interesting. There are a quad for sale on ebay. Item #200543559654
I did just notice under "Brand" it states GE
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.
There were actually Telefunken 6AS7Gs. They are quite rare. If I recall right, they have brownish bases.

OTOH, there *are* generic Russian tubes *marked* as Telefunkens!! So you have to watch it, and IMO you will not see any huge improvement with the power tubes. You are usually better off messing with the driver tubes to improve the sound, at least with our amps.

FWIW if you do find Russian tubes marked as Telefunken, they are fine tubes, no better or worse that than your regular Winged C tube, which is a good tube. I just don't think it would be worth it to pay extra for the name on the side.