Speaking as someone who used to use a similar setup, at 1080p you'd be lucky to manage a solid 30 fps, this was running a combination of low setup with medium textures. At this point, I was using 3gb RAM scavenged from a broken PC, and that was often used to its fullest, so you may well get 40fps, like chemmajorp53 said. At lower resolutions, however, you'll be looking at a respectable fps.