The techs at Brooklyn Car Audio will add a speaker here and a subwoofer there—maybe a video screen or two on the headrests—then seal it all with an alarm and send you thumping down the road. With Pioneer, Kenwood, and JL Audio products, they do everything from custom builds to simple upgrades. They can even build an advanced sound-and-video system that turns your car into a digital theater with movies for the kids, tunes for music lovers, and a GPS navigator for when you need decent conversation on a road trip. Services also go into tinting and remote starters, along with a labor warranty on all installation work.