Turn down the AA settings. 8X MSAA in that game is extremely demanding. You also won't really see any real benefit in using 8X MSAA when running a 1080p display. Anything over 4x MSAA pointless at that resolution, aside from making your GPU work harder. Try using 2x or 4x MSAA if you want to get playable performance. FXAA also works if you want to get the highest possible framerates.