I used to have a (daylight viewable tft) touch screen mounted in the dash connected to a pc in the boot and the amps & sub & stuff. Loads of wiring! DVD, TV, MP3, CD, Radio. Shut itself down when you turned the ignition off and such.
Still have the screen & pc & the cusom console surround I made - its all collecting dust now in the shed along with all the unfinished software, plans & docs!
What did I learn? If time is no problem and you have the tenacity then go with your custom build. Otherwise spend the money on a manufactured soloution.
Hth
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