Springs will make the biggest difference in handling. Some good shocks will help keep it all in check. I have both the rear TL-S sway and the TL-S upper front strut bar. I haven't installed either, but plan to when I install my new Koni shocks, they are all chillin in my basement.

I am on H&R sport springs, and I would recommend them. Cornering is much better, car feels a bit more connected to the road, and minimal ride compromise over stock.