Hello, I have about $700 to spend on a new graphics card for gaming, currently have duel core and 9800gtx 512, and 4gb of ram
More aboutwhat card help
For $700 you can get the HD5970 but that is not necessary the best solution. It is going to be based on what CPU you have (dual core is not descriptive enough), the size and quality of your PSU (power supply) and what resolution you game at (monitors native resolution).
Agree with rolli59, tell us your complete specs(CPU,RAM,Motherboard,PSU,Monitor) and we will suggest the proper card for u...