For that speed CPU, you may have a PCIe card, if you do, Radeon HD 5550 GDDR5.
If you are planning to upgrade later to a faster PC, take a look here http://www.tomshardware.com/reviews/graphics-card-geforce-radeon,2761.html and get something higher end. Unless you have a good power supply over 400watts, don't get anything over $100, you probably won't have the power to run it.
Will need more system specs before we can help. What you have listed we could provide you with lots of options but many of them would be miss guided. Please supply more details.