I replaced the stock 2" pipe and muffler with a 2.5" catback to a Flowmaster
50 series with Delta Flow technology. With the Delta Flow this is
a very quiet muffler, but when you punch the gas you (and others around
you) will know that it's not a stock exhaust that's on the car. The
50 series is one of the quietest mufflers that Flowmaster offers.
You can also get it without the Delta Flow and this will increase sound
levels inside the car, but it won't really make the exhaust much louder on
the outside.
Sound file added. Listen here
(turn the volume way up when listeing)