They were probably made by a vendor like many parts are but not considered aftermarket. There are many different exhaust combo you can do depening on your personal tastes. The best way to determine what is right for you is to hear them in person. Our next OMC meeting is 1/27 and as long as the weather is nice you could probably persue any of us to start out cars up for you. If you want to go the inexpensive route, you could always just buy some different muffs and have them welded into the existing catback. Most will buy an aftermarket catback which includes new 2.5" piping and new tips.
Borla, Bassani, Magnaflow, Blowmaster, Mac, and SLP all make catbacks for your car. It all depends on what sound you are looking for and how deep your pockets are.