I'm into Hi-Fi, not an "audiophool", and the only stock build I ever did with a 6GH8 type was a Dynaco ST70. I repinned the 7199 sockets and rolled different types and settled on a Sylvania JAN 6U8/6678. Nowadays I duild my own driver circuit with a 6SL7 / 6SN7 combo. The 6AN8 is a different pinout!
One 6GH8 type is most likely as good or as bad as the others, use a top tier brand if possible. Stay away from the cheap ITT, Lindal, ElMenco, etc.
Sorry, had to throw it in!