6sn7 tubes for Atma Sphere amp

I have heard the Sylvania 1960s GTB and RCA GTs in the 60 watt Atmasphere monos. I think Ralph likes the RCAs but I found the Sylvania richer and more pleasing. The W and TS are two that I use in my preamp,which is an AES AE3. If you have these costly tubes, then roll them, and see how they appeal to you. There is quite a bit of variance among tubes even if they are the same type. I own multiple pairs of Ws and TS RPs and only one pair of RPs is really any good. Some of the Ws are worldbeaters and some ...well they are..real losers, that are terribly microphonic. Expensive lessons in tube rolling.

1Kitch, this may be obvious but Ralph knows anything you want to know about his amps. 
In terms of reviving the thread there isn't a great deal more to add than what was already known about tubes from earlier eras.  The RCA and later Sylvania tubes are still used and in reasonable supply.  6SN7s were made by the bazillion so decent old stock tubes are easy to find with a couple of exceptions.  The only 6SN7s I can think of that are new since 2010, are Psvanes and the Russian Tung Sol.  I don't know how either of them would work well in an Atma Sphere amp. Ask Ralph he might know.