I don't have headers but it is stupid loud at WOT even without headers. It has a deeper tone to it over the people that just replace the muffler, but again, at the cost of the Corsa Sport catback, if you're just going for sound (since adding a catback system does not benefit you performance wise, even with headers), then I'd really look into just hacking off the resonator and muffler and adding a Magnaflow or other muffler of your liking.
Brand new, these systems are anywhere from $850-$1,000.