In fact, I just listened to Stompbox by The Qemists and everything is smooth all over, and that's DnB. Didn't distort any of the distinct instruments and effects despite the rather heavy use of bass.
My only gripes with the HD600 are its polite top-end (I want some more sizzle!) and the non-cavernous bass. Would have loved if it just extended a little bit deeper with more texture and definition. Otherwise, this is a fantastic headphone.