Welcome to the forums!! The BBK long tube headers are what really give this setup some great low growl...not that you can't have a good sounding exhaust without headers. You certainly can!....I really enjoy mine and I don't have headers (maybe sometime in the future lol).
But doing header isn't usually cheap either depending on what you get...the quality, shorties versus long tube,and other factors. I'm thinking this setup would run you around $900 to $1000 on parts alone, and so you'd still have installation to worry about.
But if you just want to do exhaust for now, you can get away with something nice for roughly half that cost.
If you want to do headers later on, make sure you do your research and be sure you think you'll enjoy the sound with headers. Shorty headers typically make any exhaust sound a bit better, but long tube headers can really make a crazy exhaust tone, so if you didn't want something really loud you'd need to be choosy on the exhaust you pair it with.
If you haven't yet, check out the V6 exhaust sticky thread at the top of the V6 section.
5th gen IS SOLD! 6th gen built 10/14!!! Can't wait!!