Return it!! A gtx 560Ti cab be had for less than that on newegg...some in the sub-$200.00 range after rebate. In fact they had a refurbished 260 for $100 not long ago. I just went from a gtx260 core216 to a 560Ti 448core this week and the difference is unbelievable.
You should definately check newegg, you could get the 560Ti, and a decent power supply for $266.00 http://www.newegg.com/Product/Product.aspx?Item=N82E16814130623 http://www.newegg.com/Product/Product.aspx?Item=N82E16817139028
This corsair 600watt psu and evga 560Ti are less than 250 after rebate..less than $266 before