It has been quite a while since I used an amp requiring 6sn7s. The ones with the most extended and "airy" top ends were metal-base Sylvanias, which were fairly expensive then, and they were a touch too lean for my taste and set up (Audio Note Kageki amp). I liked the Tungsol Roundplate and a copy of that tube (Neotron 6sn7). There was another rare metal-based tube, I believe a GE tube, that was lean and mean and very extended on top--I did not like it and gave it away to a friend.
