It might not be the video card making the online games lag though. If an oppentent seems to be jumping around the screen, or standing stil, for example, this could be something to do with their or your internet connection being too slow to handle the dat fast enough.
Most online games have something caled a "Ping" chart, and this tells you how fast your internet connection is compared to everyone else. The higher, the worse, and the Lower, the better.