For what it's worth, I replaced my stock muffler with a Dynomax Super turbo muffler. It cost about $60.00 shipped from summitracing.com. I think with the stock pipes you should be able to get a new muffler put on for about $100-$150.

The muffler has a little more "growl" than the stock muffler, but it is not much louder. After about 500 miles of driving it seemed to get a little quieter. I like the sound personally and would recommend it for someone who doesn't want to wake the neighbors with their exhaust note.

I have noticed better gas mileage since putting it on. (about 1MPG improvement in the city) A little more "pep" when stepping on the gas too.