1st order of Biz is to get axle back exhuast (mufflers), i love the classic throaty Flowmaster sound but theres a ton of options, try going to youtube and listening to the many exhuast combonations.
If you want to free up restriction you can get a mid pipe with high flow cats, i have the Magnaflow catted X pipe, it will get much louder but you should still be able to pass emissions. YOu can also get an Off Road mid pipe, they have NO CATS and it will get VERY loud and smell funny but free up the most flow and produce more power. Off road midpipe will NOT pass inspection, hence the Off-Road name.
If you want max power long tube header are the way to go, they can get expensive and installation is 6 - 8 hours of labor!, with Longtubes you need a matching mid pipe so you will NOT be able to reuse your stock or aftermarket midpipe thats designed to work with stock exhuast manifolds or shortie headers. Not all longtube set ups will pass emissions, so you will have to do a lil research.
This is the fun part, enjoy your quest for YOUR sound.