That’s a cool story! And when I come to think about it, I think I’ve read about that, lurking the forum ?
Yes, I’ve heard from Jeremy, who also post on here I think, that the very last, (7 or 8?) IIB KRG’s are something very special in the power section.
I run all 6L6’s as well. I’ve tried it with Sylvania STR416’s, which is nice for a change every now and then. But I prefer it with all 6L6’s.