man dont go DNX thats cheap shit. but if you are i say just go to a muffler shop get some cheap muffler with custom catback piping $200. tell your bro to just save up and get something good. if you do it , do it right the first time.
I'd tell him to save up and get a good one, but the car has NO exhaust right now. Its seriously a 1 foot pipe off the cat. lol Loud as hell, and NOT good for his first car to be that loud. lol.