An alternative to replacing your video card is overclocking the drive you already have. You can generally do this either with your graphics card's driver or with software tools downloaded from the manufacturer. As long as your computer's cooling fan, the fan on the graphics card itself, and/or your power supply can handle the speed you choose, overclocking should give a modest performance boost. Some negatives are that the noise of your fan might greatly increase, and that overdoing it could reduce the lifespan of the video card. It's worth considering if you are on a tight budget, but improvement is far more dramatic when you replace the card.