Never quite heard the difference between S9, J3, X7. Same generation, same version of EQ, didn't check the hardware, but they all sound very nice and detailed to me.
I had an original D2 for a while, and I thought it was warmer, had narrower soundstage and was less clear in the mids, although I kept it for 3 years. It may have improved with the D2+.
Edited by tienbasse - 9/22/13 at 2:58am