Computer System in Car

A friend of mine did this in his car he installed an extra batt so his power wouldnt be an issue he used a power invertor but not one of the cheap cig. lighter ones he bought the ones used in conversion vans  for the tv vcr systems. . . he then made sure that it was wired up to the batts hard wired not through the ignition system so when he turned his car off it didnt make a difference bc it still had power  obviously it eats power quicker this way but his comp had some sort of a power saver mode where it "goes to sleep" kind of a stand by sort of thing   he hasnt had any probs as long as he remebers to put it on power saver mode. . . ..hope this helps in some way

also you will need somekind of line driver to amp up the signal and maybe a x-over if you amps don't have them built in. soundcards don't have alot of outout voltage.