From what I find on your system, just about any PCI-E based GPU (video card) will meet your needs. This real issues are these:
1) What is your budget and intended use (general computing, development, gaming, etc)?
2) What is your budget and where do you prefer to get parts from?
3) What is the power rating of your power supply (label on the side of it, inside the case)?
To get a qualified answer, we would need to know these things, at a minimum.