Why not leave your Empeg installed, but put it (in its docking station) in the trunk, or under a [well ventilated] seat, and get a cheapish CCD video camera - one of the small "coin" sized ones, and mount that so it can see the display of the empeg, Then route the front or rear 4 volt left/right audio outputs from the Empeg to your new head units Aux-in, and the video signal to your RGB display that can show/see the Empegs display [admittedly in monochrome] on your head unit.

You can control the Empeg via a IR remote (with IR extender) if needed, or with a Sony wired Stalk control if you have the Tuner module attached.

If you want to go the next level up, then add-on one of the BOB-3 Video overlay modules or even simpler the XBOB display board from Decade Engineering - that will take your composite video image from your CCD camera, and overlay text information in the top or bottom half of the screen (as appropriate) where the Empeg display is not showing.
The textual information could include additional information like:
track information, current Empeg temperature - whatever the Empeg has available in /proc/* - and its all sent out the serial port of the Empeg to the BOB-3/XBOB modules serial input via a shell script/program on the empeg which starts whenever the empeg does.