Is there really any point in buying just headers alone? OP might have some other plans for his car... but headers alone? All headers do is make it easier for the waste gases to exhaust from the engine... maybe 1 - 2 kw gain at the most? It would make sense if he's looking to buy an exhaust system as well, a few more gains there and nice growl too... maybe a cool air intake too.
S.alajmi.87 Take your time, do your research and plan your parts carefully. You don't want to throw your money into something and find out its not what you're looking... or you end up having worse results than what you began with. Remember, to my understanding, any modifications like that will void your warranty at the dealer... that is if it hasn't expired yet.
Make sure any modifications you do are installed properly. To my understanding, certain sensors (O2 sensors etc, sometimes even MAF sensor) have to be disabled after modifications have been carried out on the intake and exhaust of the car. Be sure to get someone experienced who knows what they're doing to carry out the modifications for you. Best of luck.