NicoX,
I recommend you post your graphics card question in the Buying Advice forum section. I'm like tonymacx86 in this build, I use a graphics card only went I'm helping out compatibility testing. It turns out that everything I need to do with respect to graphics can be accomplished with an i7 processor and Intel's Integrated Graphics (HD3000, HD4000, HD46000). Did you see the 760 graphics cards recommended in the
Buyer's Guide?
Also, I'd recommend Tom's H/W's monthly
Best [Gaming] Graphics Cards For The Money. Be advised that the new AMD/ATI are not easily integrated (get working) with OS X which is why the tonymacx86 Buyer's Guide recommends nVidia 600 and 700 series graphics cards.