Yea, don't do a cat back. Just get a muffler. The Borla XR1 is a popular choice. You already have 3.5 inch exhaust wit the 6.2l
As for headers, only do long tubes, but you best be tuning it to really see the gains.
Run a catted long tube setup! Catless will be loud, if you run catless to save cash, it can cost you in the long run, ask me how I know! You will also need an inspection hookup.
Also, the longer case mufflers are quieter. Running a muffler with a bullet can help too.
I want your stock muffler if you get rid of it! Hell, I would even trade you.