or you can spend $80 more and get an Ultra. and get a hand selected GPU, better heatsink to make it run cooler, and it will use a tad less power than a GTX. not to mention the updated silicon work.
if you are spending $520 why not spend a little extra for the best on the market currently.
of course i dont see what is wrong with your current GTS. it should be able to play everygame at full settings. i wouldnt spend the money to upgrade just yet.