Will do
Well I'm not musician or some audio "PRO" , but I can absolutely hear big difference between the rectifier tubes. I might not be able to tell them apart in all songs, but I can do it in "problematic" ones.... since those songs just suck hard - unlistenable for me. But I can understand that there will be people who won't hear the difference, like there are people who can't tell wines apart (I'm probably one of those, since I don't drink at all) .
Ye, I heard about those, but didn't really get to looking for / buying them, since they were so expensive and I was happy with the Siemens CCa's I got. Might look around on ebay for those
But yes, the GEC 6AS7G's are must. Hope I will get to try also those famous WE 421A's sometimes in future.
I also had E188CC, Siemenses and was quite pleased with them.