I have. Bought Gold Lion KT88s from Doug's tubes for about 100 bucks, and a couple of months later one of the tubes just died. I sent an email to Doug and he recommended something else, because while Gold Lion sounded awesome, they're not too reliable. So I bought some Penta KT88 IIRC, and been very happy ever since. JJ KT88s were mud land for me (too much low mids in a bad way), and the KT77 were a fine alternative to EL34s - more low mid presence.