The GMPP exhaust is a nice piece, but overpriced and really not what a lot of people are after, performance wise and sound wise. We've removed and thrown away several GMPP kits, due to their owners getting tired of them.
Your goals, emissions, and warranty thoughts/requirements, will determine what headers to use.
Long tubes will give more sound and a lot more power, but require a tune, often voiding warranty, and sometimes going against strict emissions regulations.
Shorties will have some more power, a little more sound, but do not require a tune, do not effect emissions, and usually don't effect warranty (depending on dealer).
However, down the road, you'll most likely be wishing you had just gone for the long tubes.
Our most common setup is the Kooks long tube headers, Kooks high flow cats, and the Magnaflow Comp Series cat back exhaust.
It has excellent power gains, sounds great at idle and normal driving (not too loud), then when you get on it, it sounds amazing, with just the right amount of "look at me" volume. This setup also has no drone.
Call us for the best prices!