Thanks for all the responses. Larryken-yes, I'm using nos tubes in my preamp-click on my system to see. They made a tremendous difference in sound. More dynamics, detail, clarity... almost like a component upgrade. Eldo1968- How hot does your amp get? Does running class A reduce the longevity of an amp? Beemer-How hot does the ML336 run? How's the dependability of the 336? Thanks again all! Stan