Regarding the Russian 6N23 tubes, I can attest to the fact that they are awesome, but the year they were made and the internal specifics are very important. I would not buy just anything on Ebay described as 6N23. I own several pairs from 1974 and 1975, and they were not super cheap. I paid around $200 for a matched pair of Reflektor ’75 6N23P SWGP Silver Shields which are considered to be the very best. Prices go down from there. A matched 1975 Voskhod gray shield SWGS pair I think was closer to $100. I own Telefunken’s, Phillips, and other sought after NOS tubes. The 6N23 tubes really are that good if you find the right ones. Musical, holographic, and good detail. Just make sure you buy them from a seller you trust. Ebay makes me nervous when it comes to tubes.
There is an extensive thread over on head-fi discussing different 6922 tubes with emphasis on the Russian 6N23’s. It is a lot of reading, and many of the tubes at the top of the list are very expensive, but this should get you up to speed. It is a headphone amp focused discussion, but I use mine in my living room system and it translates.
http://www.head-fi.org/t/761078/6922-tube-review-17-top-6922-6n23p-e88cc-cca-7308-e188cc-tubes
And as others have said, you can trust Brent Jessee.
There is an extensive thread over on head-fi discussing different 6922 tubes with emphasis on the Russian 6N23’s. It is a lot of reading, and many of the tubes at the top of the list are very expensive, but this should get you up to speed. It is a headphone amp focused discussion, but I use mine in my living room system and it translates.
http://www.head-fi.org/t/761078/6922-tube-review-17-top-6922-6n23p-e88cc-cca-7308-e188cc-tubes
And as others have said, you can trust Brent Jessee.