I'm a little worried about the CCAW, copper clad aluminum wire used in the voice coil.......for example the AD2000X uses a high purity copper wire in the voice coil, 7N OFC, which is probably why they sound much better than the AD2000X. The AD900X also has aluminum mesh where the AD2000X has magnesium. I might try new AD2000x drivers, that I can get for an additional $90, I'll have to see how they sound, and then posibly try a different cable, either pure silver or silver copper hybrid. Since, these would be for home use only, Parametric EQ at 30hz and 60hz, would bring the sub bass up......I still use those settings for some of my music with the S500. Although my S500 have plenty of bass on most music, to the point the bass bottoms out with the EQ on, which distorts on music with heavier bass. I like good clean tight quality bass, but it can get overdone in a lot of poor mastered music. With EQ I can control that with one mouse click in my jRiver MC software! I listen to a lot of female vocals, and EQ on the sub bass will tame the high pitch female voice!
Just thinking ahead, I haven't heard any open back cans other than the Senn HD650, and even with a pure silver cable, they were too dark sounding as I remember, but they have been gone for more than six months. Looking for to the open sound of the AD900X, hope they can compare in sound to my modded S500's. I know my S400 with Moon Audio Blue Dragon will be up for sale. With my two S500, modded, the S400's only get used for comparisons!