Need more information, please tell us your current spec, including PSU information. Also we need a budget of what you like to spend, and any website you have a perference for or against. The games your thinking about playing etc.
I have one of these but I'm not using it right now. It will play most games fine at a lower resolution(720p to 900p) at around medium settings. How much are you going to pay for it? A 7750 or a 7770 can be found reasonably cheap and perform a lot better.