Funny...this is exactly my situation. I've seen new OEM cats online for about $100. You could go with a Magnaflow if you can find the right model, or you could get ambitious and get a y-pipe + hiflow cat setup for ~$300. I'm not really mod-happy with my powertrain, so I'm not inclined to spend the extra cabbage on the other stuff.

"Think of it, if you like, as a librarian with a G-string under the tweed." Clarkson on the Mondeo.