Graphics card for NFS RUN

your graphics card isn't the "bottleneck" i would say that you need to change everything to play that game, best solution buy a new computer.

i have tested it with with my old e8400 and the performance also was bad, so you will need to change both, CPU/GPU to play that game.

of course that if you add a good video card there youy will be able to play it, but then you will be bottlenecked by the CPU. it is going to be a waste of money.

I would say first buy the GPU. it can be something like this one if you are going to play at 720p~1080p resolutions:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
or one for a little less:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

and later when you got the money buy a new CPU also:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

you will see that the performance will upgrade a lot specially in cpu dependant games;

don't forget to make sure your psu can handle the new video card before installing it, i would recommend you if you don't already have a good one:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

so just buy a new motherboard when you get the new CPU with 1155 socket use your DDR3 ram your HDD, and you will be good to gow.