How much difference in quality on my Sennheiser 580's would I hear with a headphone amp hooked up to my main rig, if any. Am using a Marantz 2220 receiver for headphone duty and it sounds pretty darn good. Am listening now through my computer's soundcard to mp 3's right now and mp 3's aren't as bad as I thought and is actually very entertaining, I'll have to burn a cd and try it. Just got these today and the sound is great.