Short answer: That depends.Long answer: It depends on what issues you're seeing when you try to play big games or anything with a higher resolution or framerate. If you notice a huge slowdown in your framerate or any sort of image stuttering or freezing, it's your CPU since it probably doesn't have enough bandwidth to handle pulling, dumping, and loading game assets for bigger games. But if you're seeing your rig have trouble rendering out details and textures, or even fail to properly boot and load your game, you'll need to upgrade your graphics card.