Heads? A good first mod
 

OK my car is all stock besides the K&N, so would new heads be a good first mod? I know they are like $1000 but if they add 45-55 HP I'd say it's worth it. What is a good brand to go with?

head/cam/intake
 

Yes, heads would be a great first mod! Although if you are going through with the head install, you might as well throw a better cam in there to utilize the better flowing heads and bigger valves. And then there is the intake manifold. It's when you get the better flowing heads, cam & intake that your car will REALLY wake up! But if you didn't want to spend all the money at once, just do the heads and cam first. You could always swap the intake later. AFR has the best heads out there right now, IMO. But TFS & Edelbrock are great flowing heads too. Let us know what you end up doing.

what mods do you have right now. Because heads will be a good mod, but you really won't feel that extra umph wthout getting the right intake, and all the other stuff to compliment the heads.

Its all stock right now, what size should I go with? Or will only one size fit? I am prolly gonna get the intake from an explorer to go with it.

This is what I did, and was not dissapointed:
Gears: 3:73's should run you $350 installed
Free flowing cat back: O/R H or X pipe(MACS are $119, plus cat back of your choice(MAC Cat Back is $299)
K&N Filter charger Kit, do not get a CAI, just get the K&N kit that utilizes your stock air tube. $80
Pullies if you want, some guys say no due to charging problems, I say go for it, and don't swap out the alternator pulley.
That leaves you with $150, you could possibly pick up some headers for that price. hope this helped. You will love the way your car feals after, trust me.