Here is a resource to help you judge if a card is a good buy or not. The graphics card hierarchy chart groups graphics cards with similar overall performance levels into tiers. The top tier contains the highest-performing cards available and performance decreases as you go down the tiers from there.

You can use this hierarchy to compare the pricing between two cards, to see which one is a better deal, and also to determine if an upgrade is worthwhile. I donít recommend upgrading your graphics card unless the replacement card is at least three tiers higher. Otherwise, the upgrade is somewhat parallel and you may not notice a worthwhile difference in performance.

Graphics Card Hierarchy Chart : Best Graphics Cards For The Money: August 2010