I've tried the EH 12ax7 you mentioned in my Thor T1000mk2 and found their were much too laid back and dark for me.I honestly can't find a better ( neutral ) 12ax7/5751 for my ( tried many ) system than the Svetlana 12ax7 ( winged C ). I have tried NOS- Tungsram,Mullard,Telefunken,Ge. New Sovtek (all ),JJ, and others I am sure I have forgotten but always come back to Svetlana ( winged c ) . It seems in my system its the best/neutral and natural all around 12ax7 tube with the least amount of flaws....Go figure !