Take the car to a good muffler shop and have them build a system. Just put in an "X" pipe to balance the flow...
Look here...
http://www.carcraft.com/techarticles/69238/

True duals are cool but they really aren't necessary if you build a "Big Single" system. Run your "Y" pipe into a 3" single in/dual 2 1/4 out muffler. Works where space is limited and sounds just as good.