WillowTheMovieX2 is an amazing headphone. But it's also an open back so it's going to be different than the X00 and will leak more sound. The X2 will probably have a larger soundstage that open backs naturally have. The X2 has arguably the best Bass of any open back headphone which is why some people like it better than the HD650. More fun than the 650. But I'd be willing to bet the X00 Bass will be better and bigger than the X2.
JamesXX2's actually don't sound flat, they are no really dynamic as a headphone. You would think so with eh build but they are actually really good headphones. I have been waiting for them to drop here.
JamesXTry testing it against an AKG K501. You will be shocked at how inferior X2 is in every single aspect of sound reproduction - except booming bass.