I put some JJs in my Night Train (power valves only, left the preamp valves alone). The amph seemed to have a more "open" sound to it after the tube swap. I really feel like there's a noticeable difference, and it was a cheap upgrade. Lucky for me, Eurotubes are the local guys.

Good luck with your toobs, Rev! Btw, the tubes I took out of mine were Sovtek.