Tdog,
The price for an aftermarket exhaust will vary. I'm not sure if I'd go to a national chain store - but any good muffler shop could do a good job.
Tancred got a full exhaust system including headers for $475. But I've been quoted up to $600 for a similar system. Expect to shell out somewhere between $500-700. That's a good range to work with...
-Chike