For that little bit extra consider a GTX 660, [...]
Also getting a decent cpu cooler for your E8400 so you can overclock it and get more from your pc for gaming performance would be a good idea.
I ve considered the 660 but it's a bit over my budget atm and, correct me if I'm wrong, due to my limited CPU it wont be too much of a difference on the current build.
Edit: Yes I'm tempted to do that overclock (get a decent cooler first) and i ve read plenty of stuff here all that remains is to man up and actually do it. Which i'm not too comfortable unfortunately.