Stock exhausts, expecially for high-end cars, tend to be really expensive.
A flowmaster will be pretty loud, and a resonator will do more to change the note than actually make it softer (observed by trying different mufflers and resonators at the shop).
Ask around locally for good shops; they're all over the place, but unlikely that I know any in Minneapolis.
Any good place will do a lot of custom jobs and should be able to pick a non-stock muffler that'll fit and give you flow more like a higher-performance car.