I recommend waiting a little for other people to do it, then watch their videos on youtube or streetfire. This is a brand new motor, no telling what exhaust will sound like. I have been listening to terminator exhaust, since that motor is a 4v like the new 5.0. But it is just an assumption that they will have a similar sound though.
As far as a tuner, SCT is definitely the way to go. If you can only get one, I would probably pick up the tuner first. Yes, the exhaust will help with looks, sound, and power. But the tuner will help a lot with power and how the car drives. Especially if you have an Auto. There are a good amount of end user parameters that allow you to adjust speed limiters, RPM limiters, idle RPM's, shift points, etc. And you can datalog with it to make tuning easier through email.
There are 10 types of people in the world. Those who understand binary, and those who do not.