Update: Just bought a GTX550Ti. Considered a HD6770, which I think is the roughly equivalent ATI product, but they were sold out at the place I went to, so the nvidia it was. I have a case with a power supply that will run it. For the time being I'm transplanting the old PC into the new case and replacing the graphics card. Will upgrade the PSU next, then work on acquiring the other necessary parts over time. I need the video card to play D3, and I figure it'll be good enough for what I need it for for quite a few years.