I am a 3d Modeler. I am using 3D softwares like Autodesk Maya and Luxology Modo. For example in Modo, the renderer uses GPU. I am not a hardcore game player but when a good game comes, i definetely play it. For example far cry 3, bioshock infinite, black ops 2. This is the reason also for installing windows with multiboot. So which card do you suggest me? By the way i know how to install hackintosh. I did before. It just didnt like my hardware. I have a similar setup like you now. I bought rampage IV. Only the graphics card left.
Edit: I bought Zotac GTX 680 4 GB =) Now i am ready to install this masterpiece according to your great guide. Ill let you know the results in Monday. Thank you again for your great guide!