What are your goals? Aesthetics? Performance? A little bit of both? The GT is pretty limited in performance mods unless you want to talk about Top Swapping or Turbo.
Aesthically what you have listed sounds good. Glass pack exhaust would take away some of the rasp of the stock catback and slightly throatier. Other than that, it depends on your budget. You can go cheap and lightly tint tail lights, exhaust tips, grilles, etc.