My preference is for the old stock Sylvania 6SN7 tubes over the other tubes you mentioned. Sound was more clean, clear and the bass was tighter in the amps I used them with. Pricing wise they are a little more expensive than the Russian counterparts but worth it for me. If you are local to NY area I have some re-issue Tung Sol 6SN7GTBs from Jim McShane that I'd be willing to lend you to get an idea of the 6SN7 flavor. The Tung Sols are my spares should the Sylvanias break down on me. Sound wise they are great all around but my preference is for the Sylvanias.