What is the best 6SN7 driver tube?

The last pair of Ken-Rad's that I tracked on Ebay went to Mr Blume of Coincident fame. He must like them in his setup, unless they were a gift for someone else. Yes, I am a busy body, so don't start.

I've tried Brimars, Sylvania green letter & VT 231, etc. The Ken-Rad JAN matched black glass VT231's that I have gone with in my pre line section are, together with the WE300B, the best tube I've heard overall. About $125/pr...enormously musical, spacious, dark and mysterious with the best bass, bar none. That is,if you can find them... The last Sylvania 6SN7W metal base CHS that I saw went for $300. Ouch.

I just recently upgrade my Supratek Chenin to Supratek Cortese mkII which is much more transparent hence differences between tubes can be easily heard. I tried Ken Rad black glass , big bass, nice presentation but not involving. Long time ago I have bought some NS grey glass 7sn7 - unbelievable what a change, tangibility, aliveness, transparency, huge dynamics, drive, drive. Different league.
After I have tried Sylvania metal base 6sn7W similar in scene, transparency but I have lost tangibility and drive.
Somebody told me that CV2821 is special, I was lucky to be able to find a pair. It do not have drive of NU grey glass I was not tapping my feet, but it have speed, transparency, resolution I never thought is possible with my gear.
If only I could have dynamics, slam of NU grey glass with speed , transparency of CV 2821.

A wealth of info here: (http://www.dehavillandhifi.com/6sn7_vt.htm). I found their results very accurate, having tried the top 10 favorites of the survey in my Cary monoblocks. The 1940's, bottom gettered Sylvania VT-231/6SN7GT, is a VERY nice(transparent) tube. The tall bottle, 6SN7W has more bass slam and a deeper sound stage.

I recently picked up some Sylvania three hole 6SN7T's from Dave Hollander. I'm using them in a pair of Octave Audio Amps. The tubes supplied by the manufacturer had no markings. So, I'm not sure what I replaced but the difference surprised me. 

The Sylvania's three hole tubes produced a much better layered soundstage. I also was heard sounds at the rear of the stage more clearly. Previously these were masked. Finally, the transparency had increased from the front to the rear of the stage. Overall, the differences were not subtle and surpassed those of the supplied tubes and some Tung-Sols that I tried. I highly recommend that you give the Sylvannas a try.