It all depends on how exotic you want to go. If you go from headers back it will be more expensive. I had a 99 suburban and what I did was cut my cat catalytic converter off and put a high flow on then i put cherry bombs on it. it cost about me about $120. It made my truck sound like a T-Rex lives under my hood.
Go here for the cat..
http://cgi.ebay.com/ebaymotors/MAGNAFLOW-CATALYTIC-CONVERTER-2000-CHEVY-SUBURBAN-94106_W0QQcmdZViewItemQQhashZitem518d9b8f9aQQitemZ350268133274QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
Go here for the glass packs.
http://cgi.ebay.com/ebaymotors/Heavy-duty-exhaust-Glass-Packs-3-In-Out-30-long_W0QQitemZ370210063082QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item56323d42ea
I end up getting this one because the base general was getting on me. lol it's a lot more mellow until you get down on it.
http://www.summitracing.com/parts/FLO-17428/
I hope this helps and happy ground pounding.