Go to your local muffler shop and have them custom make a 2.5 inch exhuast system. When it comes to muffler choice have them hold up several different mufflers while someone revs the car so you can hear what they sound like. Pick which you like best and finish off with some tips of your choice. If you have the extra cash at the time get a high flow cat at the same time. Later on grap some headers for not only the extra performance but also to make it sound deeper.