I have a very good working setup (see my signature) I am thinking to buy a more better and powerful video card but I don't want to damage my configuration, does anyone know if I change my video card, OS X will still loading? I am scared

Don't be a chicken ! Experiment ! That's the way to learn new things. In the worst case scenario (assuming you are using the wiki to choose a supported card ) you will get a vesa unaccelerated image and wrong resolution untill you find and install the proper drivers , but OS x will still load. In any case you will still have the old videocard around to put it back in the unlikely event you will get a blank screen.

Don't worry so much , it's not heart surgery

Marius