Great question. I love my KT77 for my QS Mono 60's but got rid of my KT 150's. Now I'm looking for KT66 as well.
Tube suggestion for Quicksilver Mid Mono Blocks
After switching from KT88's to E34's (with which I had a mishap), I installed GL KT77's and they are doing quite well.
I just posted 2 sets of KT88's for sale on Audiogon (A matched quad GL, and a matched JJ quad).
Im thinking of getting a set of GL KT66's for rolling.
Anyone have comments on the differences between the KT77's and the KT66's, and what happened to the 6L6? And maybe a comparison between the 6L6 and the KT66.
Thanks
T