So my tried and true AVIC-Z2 (updated to Z3) from about 11 years ago is finally starting to get tired.  The display motor is intermittent (when the temperature is warm), and the backlight has become quite dim.  In searching for a replacement unit, I've settled on either the 8400NEX or 8500NEX.  I understand that the 8400 is discontinued, and has been replaced by the 8500.  My question is whether there is a compelling enough reason to shell out the additional $475 for the 8500?  I've been unable to find a comparison of the two models, and even on the Pioneer website it isn't all that clear (or at least doesn't seem like much of a change over a slight difference in screen layout).  Finally, while there were methods of changing a Z2 (or Z1 for that matter) into a Z3, is there a way to give the 8400 the look and feel of the 8500?

Only different is in software. Weblink instead of AppradioOne. And you will have rear camera guidelines.