Didn't realize you were just up the road. I'd do the work if you need someone reputable.
Personally I don't believe you'd notice a difference between headers and plog on the level you are looking to go. I had plog/DP when my Regal was SC'd, Gen V and 1.9's....Never held it back at all, actually that setup led 05CompGman to cam and others to do stuff as well.
Sound.. there is a slight difference, morso a little louder in the cabin as you get rid of the double wall stock downpipe.
CAI etc.. I've toyed with this in various setups/cars that I've had. I dislike the noise of a cone when the car is cold, and yet run one. I've also run the stock airbox with the Gen V/Rocker setup mentioned above and never had an issue getting enough air.