This should be a decent enough upgrade, will be able to handle games nicely up to 1080p. http://www.newegg.com/Product/Product.aspx?Item=N82E16814161338&cm_re=5770-_-14-161-338-_-Product
May i suggest you upgrade your PSU however? Nothing too special, maybe just a 500 - 550W unit from Antec, Corsair, Silverstone or Seasonic? I only say this because if you have a generic unbranded PSU, they are of questionable quality and if they blow then your whole system does, including your shiny new card.
The choice is yours however.