I would check into getting a high performance one, like a Random Technologies for example and doing the exhaust from the header back, or even putting headers on at the same time. I prefer doing stuff as units like that, makes more sense(did the entire front end of the bug at the same time for example), if the money is there to do it. If you get the parts, a reputable exhaust or muffler shop could do the install if you don't want to do it yourself.