My first carputer was cheap as free. It featured an old compaq mobo i had lying around with a celeron 460 processor. It was powered by power invertor and fm transmitter I both allready had. I built the "shutdown controller" myself and the controls were a hacked up joystick mapped to control winamp. Not very exciting but it was an "mp3car". You'll find pretty quickly though you want more. I soon added a touchscreen ($300) then gps ($100). The power wasnt stable enough so i switched to a new invertor ($70). Next i needed wifi and antenna ($50 and $10) followed by XM ($50 and change). Needed a slim drive up front i could put dvds into (rather than the old full drive in the trunk) ($80) and of course with all this new functionality i needed a processor that could actually play a vis without choking. That's when I bought an epia and moved everything into the dash (Mobo $130, Adapters plus $50, Power regulator $70, Bondo and more $40). Total cost... Free + $950. Can you make an mp3car for cheep, sure, can you pursue this hobby for the same price, not a chance.