I recently found a deal on a new SVT AV series Ampeg head and after playing it through an Ampeg 6x10 cab I quickly traded my rig and made the new rig happen. I didn't do much investigating though before hand because I just ran into this rig and really fell in love with it. Are the old SVTs and the new SVT AVs identical amps or have changes been made? If so, what changes and are they good or bad changes? Are factory tubes on new SVT AVs ok or should I get new tubes? Thanks.