Just got a voshkod 6n6p & and an amperex 6dj8. So far I'm enjoying the russian tube, I think it has improved imaging over the stock tube and my TJ fullmusic 12au7. Mids are quite "sweet", I'd say vocals sound more lush. Currently enjoying Gabrielle Aplin on my Fidelio X1, great match
I'm also hearing a boost in mid-bass and increased soundstage depth. Might be a bit too punchy with the x1..
I have about 25 tubes and and I really like about 20 of them, but right now the 6N6P is my favorite.