Not knowing your exact budget will make it hard, but let's stick to around $200, shall we? For $200 you could get yourself a pretty decent graphics card, something that would be faster than your current EVGA GeForce GTX 460 card.
NewEgg offers EVGA's SuperClocked 2GB GeForce GTX 660 card for $229.99, alternatively, you can get a HIS Radeon HD 7870 GHz Edition for $229.99.
Both cards would use less power, be quieter, and run much cooler than your Fermi architecture-based GPU. I hope this has helped your decision!