oh man screw all those places, your local welding shop, buy 4awg for a $1cdn a foot, if you can weld with it, it'll sure as hell power your car audio

running that throughout my car, power and ground, of course not all amps accept 4awg very easily hehe
oh and one more note... the stuff is damn flexible, and make sure u have some big cable cutters or a hack saw in order to cut the stuff hehehehe, there's no way you can take some dinky *** method to cut it, the strands are strong, but Very flexible, tie the sucker in knots easily