Welcome. Sounds like you got a steal. You got a couple of options for an aftermarket cat-back exhaust. Check the posts this category from Aaron Garney about the system he's offering - looks very nice, everything Aaron offers seems top quality. There's also Brullen and I'm sure someone will post contact info. If either of those don't suit you, then you can easily get a local shop to fab a decent system. I recommend a 2 1/4" pipe, Magnaflow muffer and either a vortex tube or resonator between the cat and the muffler. Avoid chambered mufflers like the Flowmaster.
Phil D.
Phil D.