Buying a video card is a lot like buying a motherboard. There are all kinds of Mfgs. out there that use for example "Intel" chips when producing a mobo. The same can be said for a video card. Nividia them selves are not the ones mfg all those different cards you see, but rather the "key" components.
In order to really make any kind of evaluation on a Nividia card one must look to the mfg. of the card and research the quality of their products. I my self have a Nividia 5700 U3 card. If you looked that up on Google you'd find pages and pages of info on it, how ever it's relavance would be some what tainted. On the other hand if you looked up Albatron Nividia FX 5700 U3, you'd find very specific info including reviews and overclocking tips. from that one could research and make a reasonable assumption on what to expect.
