One of the options that you can buy it with today is the AMD Radeon HD 7770. So I would say that would be your best bet. It will be fine with that same PSU. Heres the one I think you should get considering it has 2GB VRAM which is much better than 1GB and its most common today.
Asus Radeon HD 7770 2GB Overclocked
Overclocked means that the default/stock settings and build are overclocked compared to a standard one. You can probably easily overclock this without problem and get more out of it. Plus its only $150 ^_^
**P.S: I had to look up the things is comes with considering they're aren't any specifications on that Mobo it comes with, unless you took apart yours and looked at the Mobo name**