If you are wanting to get over a 5.9, you will need to run your OS from a SSD. There is no mechanical hard drive that will score over 5.9 (unless the new WD 600GB VRaptors do??). My WD 300GB VRaptor would only score a 5.9 and it was much faster than your WD Green 1TB. If your system is feeling slow, you could to look to go with a SSD or a Samsung Sponpoint F3 500GB. They will add responsiveness to your system. The "WD Green" drives were not meant to be truly boot drives but lower energy storage drives.