The amount of ram on the card is not the primary consideration, but only a choice to be made when more important decisions have been made.
An ATI 9800 pro for instance, is not in the same league as a NV 6800, no matter what ram is fitted.
The RAM quality actually has more effect on performance than quantity as well, but this subject gets a bit techy.
Suffice to say that different manufacturers use different quality components, so careful research is needed to make an informed choice.
Performance comparison charts between the various video cards are an easy way to shortcut the research, but beware, the card you buy may appear to be the one you wanted, but check the fine print carefully. Let the buyer beware.
Prices can be misleading also, use this site as a general guide, once you have made a choice.
www.pricewatch.comGood Luck


Mainboard: Asus P5K-Premium, CPU=Intel E6850 @ x8x450fsb 3.6ghz, RAM: 4gb PC8500 Team Dark, Video: NV8800GT, HDD: 2x1Tb Samsung F3 RAID-0 + 1Tb F3, PSU: Antec 550 Basiq, OS: Win7x64, Display: 24&