The difference in speed between 1333 (what you now have) and 1600 is small. I would leave it alone. It's not the reason your frame rates seem low. I use the windows disk clean program at least once a day, along with ie privacy keeper version 2.73 to keep my system running smoothly. Your system may also have an aftermarket virus protection program. Some of those will slow your system down, such as trend micro. I only use microsoft security essentials. You can try it for free, but you must uninstall your old virus protection software first, which may cause other unforseen issues. If your system is running smoothly, I would leave it alone for now.