You can still get high flow out of an exhaust without it being overly loud.

What is your exhaust setup at the moment? Knowing that we can give some more useful suggestions.

For example assuming you are running a 2.5" downpipe, you can get a Carsound high flow cat with a 2.5" inlet and 3" outlet, and then run a Thermal Turbo 3" catback. As it comes from the factory the Thermal has no resonator, but you can have any competent muffler shop add an 18" long resonator to the mid pipe which will quiet things down nicely.