The game is more taxing than the photography. I looked up the recommended requirements, and you're probably looking at a little under a $100. If you want ATI, an HD4850 will do. For Nvidia, GTS 250. Either one of those will give a you the cheapest card that fits with your PSU and can play your game smoothly. You can go faster, but it's probably better to go with a lower-powered card due to possible cooling issues in your case.