if you want to gain horsepower as well as sound, then you want a "true dual" exhaust system... here's your options...
you can either start from the engine and replace the entire exhaust system with headers (long tube or shortie), h or x pipe, mufflers (borla, spintech, flowmaster, etc,) and tail pipes (or get GT takeoffs online, you get gt mufflers and the polished tailpipes, they look nice) ...this is especially good if you'll be doing extensive engine upgrading in the near future...
but, if you're not at all, or not within the year, what you can do is take your car to a performance shop and have them cut your exhaust off after the stock catalytic converters. they can weld on an h or x pipe on and you can get the gt takeoffs or pick your mufflers and tailpipes. this is the cheaper option, though it has less potential than a full exhaust swap. you'll have 2 or 3 less hp right away too. but then, this is the way to go if all you'll be getting are bolt on mods...
if i managed to confuse you, i'm sure one of the other guys will help straighten you out...
peace