Your current power supply specs, budget and what do you want it to do would be needed before we can make good suggestions.
Your motherboard would take A GTX590, ATI7990 or GeForce Titan ,but they are all around $1000 and would be severely hampered by your CPU.
And with that old of a machine your power supply probably would not cope with either of them also.
So a little more information is needed from you to get a good suggestion.
MC= Media Center?