no offense guys, but i would very much like to say "KISS" (Keep It Simple Stupid) hahaha, just kidding...
let me tell u wot i've done already in my car...
- fixed a laptop, onto the ceiling, just close to the back view mirror.
- used inverter (500W for Rs. 1200) & the original charger, both set up in the dash board.
- used a stereo cable (which is actually called male-to-male in terms of its connectors) taking laptop output to my headunit's rear AUX input (did the routing myself)
all i have to do now is to just play the playlists that i have.
now comes the most amazing part, i control volume/tracks(next/previous)/play/pause/stop etc from my mobile 
yeap, u read that right, i have I-Mate JasJam, and i use a Computer-to-Computer (already setup & paired) WiFi network between my laptop and the mobile for audio control....
wanna see the pics???