Difference in comparison to what?
A bass boost and soundstage enhancer like the ones on the iCan would be nice - I wish I had them on my amps. I would probably use the level 1 bass boost - I'm happy with the amount of midbass on the HD600, but subbass extension could be better.
Exactly this. While the Senn's so far have been amazing some improved sub bass would make the movie/gaming experience so much more immersive for me.