Bazy.......Depends on what games you want to play. I am going to buy the 560 Ti Twin Frozr cuz of its price (MSI $200) and it plays Battlefield 3 on High with good frame rates. But like inzone said, the 7850 is a step up....but it comes down to price for me. I'd have to spend another $60 to get the 7850.
With that said, if you're not in a hurry to buy then if your willing to wait then you could buy one of Nvidia's new platform cards (Kepler). They will be better than the (Fermi) series, but when can we buy them? don't know.
Check out AnandTech benchmarkshttp://www.anandtech.com/bench/Product/549?vs=547