Of what I have experience with, I liked these...
Tesla EL-34 (vintage) - Marshall JCM-900
TAD EL-34B STR - Marshall JCM-900
JJ KT77 - EmerySound Superbaby, want to try in my Marshall, but requires some adjustment
EH 6CA7 - Orange AD50
Valve Art KT-66 - EmerySound Superbaby, Wallace BKW-45...