I haven't heard Cowon DAPs and I'm not anywhere close to a sophisticated audiophile, but my impression is that, with a good amp (presuming you have good drivers to amp), there's much less distortion, which creates a much more defined, specific, clean sound - delivering it much more accurately at any actual volume of listening. As an example, when I listen to my mg6pro through my SR-71B in balanced mode, at what I consider equivalent volumes, compared to running it straight out of my iPod nano without an external amp, it sounds immensely more dynamic and powerful.
Nice, the biggest vent really opens the sound stage up a lot and more air is being felt especially on hard sub bass electro and breaks. Feels like a ear massage or warm rolling bass. I have been thinking of a portable amp even though this Cowon has some good power. Maybe a amp will allow the bass to be pushed better man my ears are ringing from the amount of bass even though my ears have continiously been ringing for the past 20 yrs. Now they are ringing louder.