Exhaust is largely just going to be louder. Most CAIs are really hot air intakes and don't help, although I think there is one AM CAI that actually helps a bit. The OEM intake is a CAI, and works very well.
I would suggest that you think about what sort of vehicle you want, what want it to do well, before doing anything. For instance; I want my car to be both to drive, but to retain it's Grand Touring capabilities. I want it to drive like what I imagine an Aston Martin drives like. So I'm focused on NVH, suspension and brakes, it's got enough straight-line performance with nothing but a tune.
So take some time to figure out what you want your car to be, what you want to do with it, and then go from there.
2012 GT Premium, Brembo PP, MT82, 3.73s, Blk/Blk. Bama 93R, Koni Yellow Rear Shocks, Hawk Ceramic pads, Luxurious & Plush Floor Mats