Is it possible to just spend the gift cards at Best Buy (say on a television or something) and then just return the thing for a refund? In many states if a gift card or gift certificate is purchased with actual money (as opposed to the gift being a prize that the store gave away), then the stores have to treat it as money and can't have an expiration date, for example. If you can get a refund out of it, then I'd recommend you do that and get your auto sound components elsewhere.
I'd keep the stock head unit if you have the steering wheel controls, and replace the speakers and factory amp. Maybe get a 4 channel amp to drive both the rear and front speakers.
97 SE, teflon wiper blades, Dunlop Sport A-2 tires, Leather steering wheel cover, Pioneer DEH-P480MP mp3 CDRW head unit, Pioneer 12-disc changer, iPod hookup, Boston Acoustic 3 way 6x9'*, Boston acoustic separates in door pods, Alpine 4 channel amp in trunk. Magnaflow dual outlet muffler and Ractive stainless tips. Autozone rice pipe and K&N 4750 intake kit. Clear corner lights. Energy Suspension end links.