What flowmaster stuff should I get for my 96 Jeep Grand Cherokee v8?

Should I get a muffler? Should I get an exhaust system? What are the benefits of each? What type?|||I have a 2003 dodge dakota with the 4.7 V8 and i just put a flowmaster 40 series muffler on it, then ran 2 pipes out the back of the truck. It sounds great and looks great. I bought the whole thing on ebay for like $200. Me and a buddy just installed it in a few hours. I don't know what size motor is in the jeep, but they're both chrysler so they're probably similar.