You have a nice system. Don't obsess with scores.
Unless you really need better performance for certain games your system should run all games nicely. Depending on the game, SLI will give you between 0% and 80% improvement. I'm guessing the average of many newer games would be a 50% improvement (or same framerate but better graphics).
Remember to use VSync if you are going much above your refresh rate (60 for flatscreen).