If you really want to maximize what you already have, than what you really need is a tuner. An exhaust may help, but there are many new areas of this DBW throttle system that would suprise you. If you dont have a tune that can take advantage of its shortcomings, then you can do all the bolt ons you want and never get all the power out of them.
If you get wider tires (and keep the same overall height) all youre really going to do is increase your rotating mass, making it harder for them to turn. The time you need to be concerned about tires is when you can spin them for 2 seconds from a stop WITHOUT power braking. Traction is an issue with any car, even in a FWD where the weight is over the front tires, as you start to move the weight shifts to the back and the front tires can break loose. In any application where you NEED a good launch, dont powerbrake it.
Hope Ive helped some!