I put these 6SN7 varients in my Wright PREAMP several months ago and could not be happier with how quiet they are and how much more spacing(air) they added to my sound stage.
I had tried 4 very good and in some cases expensive NOS 6SN7s but were finicky and some times noisy until they warmed up. They sounded good but these treasures sound better.
The treasures run very cool as well.
I added a quad of the KT-88s to my Wright power amp which was a nice upgrade but not like the CV-181s.
The wright amp uses 6 6SN7s on the input side. I received 6 CV-181 treasures a couple of days ago and put them in the AMP.
I was using some JAN Phillips that were quiet but the treasures further improved the sound stage, more air but the big thing I have noticed is how quiet or black the background is if that make sense.
Anyway, if you use 6SN7s I highly suggest trying some of these Treasure 6SN7 varients.