Like everyone said, please get a SSD. You have a kickass system already. It's best to have your operating system on a SSD for ultra speed so if you get one later you will have to reinstall Windows all over again. Think of the hours and GBs of Windows and MS Office Updates... the horror!!!
You don't need one too big, just enough for an operating system and a few programs. At the rate of SSD price drops, it's really affordable now.