I'm using an older RCA 5y3 which I prefered to a sylvania which was the only other tube I've had in that position..
The CBS's I got were from ebay a while ago...I did not pay much for them.
fwiw, I did notice a pair for sale @ 75.00 (I think) from a guy in ebay 'stores'..the right ones..50's vintage. there's another, probably 60's vintage cbs, has a horshoe type getter, but much closer to the plates than the older ones... the latter is v good imo, but not quite amazing..
I thinks the guy on ebay has both btw .
I have telefunkens in my preamp, but haven't tried them in the cornet...
the tungsrams just have a tone that I really like. They're crisp, clear,, if a bit lean, but v hight output + powerful sound...
I have contemplated putting them downstream, so I may try the tele's yet.
fc