Just because a graphics card has a lot of RAM DOES NOT mean it is powerful. Generally a card with more RAM performs better but it is not the most important factor in its performance/speed. A good graphics card has a good GPU (graphics processing unit) which is what accounts for the cards processing power.
My dad found a 4 GB card
I have never seen an mainstream gaming graphics card that has 4GB of ram in it, the only cards that I have seen with that much RAM are professional workstation graphics cards, which fine for gaming, but they have the same performance as a gaming graphics card that costs 1/8 of the price of a workstation graphics card.