@estreeter-I have the Japanese model. I really do listen to my phones, at times, way too loud. Without the sound enhancements, it is definitely better.
I use strictly IEMS. Heir 8.0, Aurisonics ASG2, and Tralucent Ref 1.
Maybe it is that I like the punchier bass like planemaker said in his post... Maybe it's time to revisit the zx1 without an amp again... I just know I prefer to have it amped, where as the X3 I am happy without an amp for sure. Don't get me wrong, zx1 sounds better than the X3, it's clearer for sure, but X3 by itself has that little extra oomph that I enjoy. Usually when I can not use an amp, is when I need it most, i.e. at the gym in a loud environment, where loud, screaming music gets my blood going.