Can you post the rest of your rig? We need to know which power supply you´ve got, as the video cards are dependent on PSU wattage. Also tell which is your CPU, so that we can recommend a card that won´t bottleneck your CPU.
Anyway, assuming that all is OK with your rig, then at that price range the best you can get is a GTX 670, as suggested by sarinaide.
GeForce GTX 670 2 GB Review http://www.tomshardware.com/reviews/geforce-gtx-670-review,3200.html
This one is 4GB 256-bit -- EVGA 04G-P4-2673-KR GeForce GTX 670 http://www.newegg.com/Product/Product.aspx?Item=N82E16814130785