If you really want to nitpick, the power wire is sufficient as well. I wired one of these decks like any other deck and ran it for a week, then upgraded the power wire...no difference. Why you ask? The radio can only pull as much current as the wire will allow. Now if hte radio wire is skinnier than the aftermarket wire you wired to it, how is the HU pulling more power? Plus, ground wire DOES matter. It's like running a river into a pond, then only allowing a creek go out. Don't you think the pond will overflow? Yup... But that's ok, I'm wrong as always right? What do I know? hahahahaha Whew, I'm impressed by the advice given on some sites...