I have a Gateway FX tower, which has served me well for 3 years. It is a q9300 quad core that came with a 9800 gt card and a 400 watt psu. The 9800 died on me last week so I am looking into a new card in the 100-120 range. I have learned that I will also need to upgrade my psu. From the research I have done I think a decent card will be a XFX Radeon 6770 (95 bucks on new egg). I have no idea on the psu. Thoughts and suggestions plz.
The Radeon HD 6770 will work fine with your 400 PSU especially if you were able to run a 9800 GT off of it. I think the HD 6770 will provide you around 50% - 60% higher frame rates on average using the same graphic settings.