IE80 is much closer to X2 in 'personality' than 600. It is kind of unfair to compare IEM to full sized opened cans, but I still feel the overall sound signature of the IE80 closer to X2 than to 600. IEMs and full sized cans obviously give a very different listening experience, but I can say the followings to compare: IE80 has tighter, more refined bass, with better low end extension. But that is about it. X2 sounds much more natural especially in mids and highs. IE80 feels a bit 'synthetic' in comparison. X2 is airier, sounds much more 'speaker-like'. IE80 has great space, imaging, layering for an IEM. But still far from the openness and naturalness of a a full sized opened can. When I listen to X2, I don't really miss IE80s bass. But IE80 is more than a great compromise on the go. IMO no IEM will ever beat the listening experience of an opened full size.