Absolutely worth the upgrade.  The basic platform is sound.  The Extremes take it to a xxx killer amp.  The SE is that last little bit that really makes things sound 'real'.  I've had older Audio Research, Rowlands, Brystons, CJ's, etc - by far the best amps I've owned if you're not running silly efficient speakers that you can run with a 5W SET.  Took my Dynaudio's to a whole 'nother level to the point where I stopped thinking of trading them off.  The only amp I've ever heard that came close was the big mono Sim Audio's.  The littler beast that I sell is very nice and sounds almost as good - but doesn't have the beef if you need really high power.
Bryan