I am sure the C3g tubes are better. Thing is, I am happy with the 6BX7 tube. I am going to try some similar variants if I can get a good price.
As you suggested I am burning in the tube. Don't know how much an effect the extender/socket saver adapters have on sound, but they look cheaply made and are only supposed to last 200 times for changing the tubes . They are not deep enough to completely insert the octal adapter 9 pin bottom pins, and there is is a 2 mm gap between the adapters. Maybe good for ventilation LOL?
Thanks, mordy, for encouragement/solace(!) re the C3GS tubes - I'm sure mab1376 is equally comforted!!...Let's not forget CollectoR13, who has also joined the club (and was very impressed with them...).
As for adapters AND extenders, I can't help feeling they must degrade the signal somewhat, which is why I persevered with making my own, using solid silver wire - acting also as the pins. But I can understand a reluctance to shy away from the task!
Good luck with the other 'variants'...