is that your board?
What resolution do you play at?
I'm pretty sure OC CPU will greatly increase your PC performance (3.0GHz or more).
Otherwise, if you really want GTX590 then upgrade your PSU seems a must, that's a very power hungry card (2x8pin).
Do not think about bottlenecking, maybe GTX590 is a little bit overkill for your system, but you're still can use it in your next gaming PC in the future.