I have collected tubes for my highly modified Rogue Audio Stereo 90 for over 10 years. Most NOS tubes came from hamfests and the tube dealers that support them. The Rogue can use KT120/KT88/6550, KT66, KT90, EL34, KT77, 6CA7 or 6L6GC for output tubes. The drivers are 6SN7s, and input tubes are 12ax7/5751. My preamp is a modified Audio Research SP14 and speakers are the very revealing Acoustat Spectra22 electrostatics.
In my experience in my system:
Best output tubes: GEC KT66, EI KT90, Gold Lion (reissue) KT66, PentaLabs KT88, Russian NOS 6P3S-E, Tung Sol NOS KT88 solid grey plate
Worst output tubes: Tung Sol (reissue) KT120, EH KT88, Mullard NOS EL34 xf2, EH6CA7
Best drivers: Sylvania 6SN7W, Sylvania VT-231, Sylvania 6SN7GT bottom getter three hole plate (badboys), Tung Sol 6SN7WGT, National Union black glass, Russian 1578 hole plates
Worst drivers: Sovtec 6SN7, EH 6SN7, Ken Rad VT-231, RCA 5692 redbase, GE 6SN7 GTB
Best input tubes: Raytheon 12AX7 blackplate square getter, Siemens long plate 12ax7, Tung Sol nos 12ax7 square getter, Matshushita 12ax7 45 degree getter, Sylvania 5751 blackplate, GE 5751 blackplate, Sylvania goldbrand 5751 grey plate gold pins
Worst input tubes: Telefunken 12ax7 (ribbed and smooth plate—- sorry guys!), EH 12ax7, GE 5751 grey plate 2 mica, Sovtec 12ax7
Obviously very gear and listener dependant. The listed tubes are neither bad nor good, just what sounds best to me in my system. Although I would suggest those stuck on Tele 12ax7s and Tung Sol KT120s might want to try something else in their gear for variety
Enjoy the roll!