[feldon34]

Even the briefest of web searches will reveal massive criticism of the 5xxx series of nVidia cards. They really fell on their face with that series and ATI took full advantage of their weakness. Of course nVidia got their stuff together and came out with the serious 6xxx series. I have a 6800 XT 512MB and love it.

One thing to watch for though is value priced 6xxx series cards. It is almost impossible to tell looking at the box whether you are holding a card that is severely crippled either in memory (some have 64MB on board and use 256MB of your RAM, also some use cheaper RAM like the 6100's and some 6300's which use DDR1 instead of DDR2 or DDR3), GPU (some have memory pipelines intentionally turned off), or bus speed (some are really hobbled).

Unless you can heavily research what you are buying, I wouldn't get any number under 6400. And I realize you are in a strange situation where your motherboard has neither AGP nor PCI Express.