Well seeing as how there is not that much to gain from intake or exhaust and because it is probably best to hear them in person. I recommend your first "mod" be adjusting the headlights. Ok, it's not a mod but it is something you will probably want to do as the factory seems to aim them low.
The next mod I suggest in a shift knob, unless you are fully happy with the stock one, at least it is something you can see and touch every day and wont cost to much money, compared to other mods.
If your heart is set on intake or exhaust, I recommend doing a search for peoples opinions as I know there are probably 2 active threads about them and at least two dozen older ones.
Everybody has their favorites, some of the popular brands for this are Nismo (Intake & Exhaust), AEM (I only and the same as Nismo), Injen (I&E), Borla (E only), K&N (I only), Stillen (I&E), Greddy (E only), Fujitsubo (E Only), HKS (E only), and I am sure many more.
Chris