I say let's revive this thread; there are more people now than ever looking for the best sounding 6SN7 tube and now there are more choices than ever with so many Chinese companies now making tubes and tube amplifiers. Psvane, Shuguang, and Linlai are all Chinese companies making very good tubes. I'm using a Shuguang CV181-Z tube for my 6SN7 tube and a NOS RCA 5691 tube for my 6SL7 tube and they sound very good together, The Shuguang is softer and a little laid back while the RCA 5691 is warmer and more forward sounding so they complement each other nicely. The Shuguang is really a 6SN7 tube labeled as a CV181 tube and it draws the same heater current of 600ma as a 6SN7 tube and not the higher 950ma heater current that the old Mullard CV181. The RCA 5691 does have a heater current of 600ma which is higher than the 300ma of the 6SL7 tube so you need to make sure your transformer can handle the extra current. My Chinese made RFTLYS A5 tube amplifier has pretty beefy transformers and it doesn't seem to have any problem using the 5691 tubes in place of the 6SL7 tubes. The transformer is only getting slightly warmer than before; it is not hot you can leave your hand on it for as long as you want.
For those of you that are into NOS tubes, I've discovered a treasure trove of information that is still available on line.
All 20 issues of the Vacuum Tube Magazine are available on line in .pdf format and can be downloaded for free.
http://www.enjoythemusic.com/diy/0414/vacuum_tube_valley.htm
I found a listening test done on many 6SN7 tubes back in 1999 on page 9 of issue #11 which gave each tube a numerical score.
The top six scoring tubes were:
The Mullard CV181 (ST shaped 1952) score 97
Sylvania 6SN7W (metal base ring, top getter early 1940s) score 97
Raytheon 6SN7WGT (brown base 1950s) score 96
Sylvania VT-231 (bottom getter WWII era) score 95
Sylvania 6SN7GT (top getter, black base early tri-plate 1950s) score 95
GE 6SN7GTA (1953) score 94
https://web.archive.org/web/20131122141643/http://www.jumpjet.info/Pioneering-Wireless/eMagazines/VTV/VTV11.pdf