What you buy depends alot on your other Hardware too. A 580 would be great, SLI even better, but you will be bottlenecked by your CPU...just something to consider. Without question, for a single card, the 580GTX a superslocked even better, is the way to go, cost aside. I don't know if you overclock or not, but OCing you cpu would help any bottlenecks, but if you have no clue on OC don't try it unless you can deal with the consequences!. Overclocking the GPU help alot as well. I use Evga cause they warranty their cards even if you overclock, My 2 cards are way higher than stock, could go higher as well. Every little bit helps!!