Is this going to be a DD? AutoX? Just a want a little more fun out of whatcha got?
Suspension, wheels and tires will make the most noticeable improvements without going to crazy and voiding warranties. Headers and a cat back will sounds good but the gains are on the low side.(but the sounds is gooood,
Since its a new car and if you plan to keep it an extended amount of time I would suggest heat management and over all efficiency.
If you have too much $$$$ and its just burning holes in your pockets (aka you can afford to be without the car,) you may want to look into supercharging.
It will take deep pockets to have this done and or EXTREME amounts of research and work.