Short ram will be good on that car, although you might want to just bite the bullet and get a cold air - they are ridiculously easy to install on a 5th gen.

From the intake, you can probably only expect 1-2 actual HP, although it will "feel" like a lot more due tot he nice sound and added punch at higher revs.

Supposedly (though I can't say for sure, as I never had them on mine), headers give pretty impressive gains on F and H series motors... I've heard people claim 10-15 HP, but I'd venture to guess it's really more like 4-5 MAX...if that. As a general rule of thumb, "mental horsepower" is about three times the actual gain. Gotta remember that.