Good Tube Selection for Atma Sphere S30?

Russian power tubes are fine! The only Russian 6SN7s worth looking into are vintage made in or before the 1960s.

I was on Sophia Electric's website and saw they carry 6SN7's for $100 apiece. That seems pretty steep and I don't know of anyone that has used them. Just mentioning another source for you.

Thank you. Great information

The Tung-Sol 6SN7GTB Reissues are considered to be among the best current production 6sn7s - you can get them for about $20 each.

Agree with several of your other posters. No need to change the 6AS7 output tubes. Play around with NOS 6SN7's in the first row first. To be honest I've noticed less of a difference with tube swapping in my S30 than most of my other amps. I'm not saying there is not a difference - it's just more subtle. Don't expect night and day difference. The S30 really does sound very nice out of the box.