My $,02 worth here. I have a pair of Quicksilver Mid Monos that allow for me to run almost any tube that is octal based. I have used JJ KT77, TungSol KT66, TungSol 7581A, JJ and EH 6CA7, and Gold Lion KT66. To me, and this is me and my gear, the TungSol KT66 is better all around than the GL KT66 as the TungSol sounds a little less "congested" as the GL tube can to me. But the big winner here is the TungSol 7581A. As much as I love my TungSol KT66 (huge soundstage, wonderfully full and warm mids, with deep bass and tantilizing highs without the hard sound) the 7581A does all of that time 10! This is an amazing tube! I have also tried the TungSol KT120 and I keep going back to the 7581A! The Mid Monos are supposed to be about 40wpc with the 6L6 tube and its variants. Well, you sure could fool me as I feel I have a lot more power than that and my speakers are not all that efficient (87db). If you can get away with the 7581A, I would do it. Viva Tubes has matched quads for about $90, a bargain. I like the 7581 a lot more than my NOS Sylvania 6L6GC, a whole lot more, and the TungSol is not nearly as hard to get.
Okay, so that was like $.50....Sorry...
Okay, so that was like $.50....Sorry...