A Good graphics card for games like rift?

Hi! I have a... HP pavilion elite HPE-400y pc. It does good with most games. I was thinking about upgrading the graphics card. Right now the one in the computer is a :: ATI Radeon HD 5450 graphics card w/ 512mb DDR3 dedicated graphics memory :: Now people are telling me a Geforce by Nvidia or whatever the brand is, is a bad one. And suposivly a EVGA geforce GTS 450 FPB 1024 MB GDDR5 PCIe 2.0 Graphics Card would be a nice upgrade could anyone specify or maybe give me a better option that isnt above 250 dollars. Now that im getting into rift I would just like to have my setting on ultra like im use to :).