Graphic cards usually need at least video memory of 1GB RAM even though the best computer graphics cards for gaming have a memory size of 4 GB or more and a relatively high memory bus width. A graphic card that has a large memory bus and bandwidth usually provides for simultaneous processing of graphical information. Currently the highest memory bandwidth available in the market is the 384GB with a memory bus width of 512bits.
Rendering and Display
The latest rendering technologies be they nVidia or ATI do adequately accelerate the rate of communication between the computers CPU and the graphic cards GPU. The more CUDA cores a card has or ATI stream capabilities the better or more powerful it is. Current cards are even offering 3D capabilities that make the graphical display experience much more memorable.
For display interfaces, the best cards currently include either or both HDMI and DVI connections. Most cards implement dual channel DVI, these interfaces fully support high resolutions that are currently in high demand due to the prevalence of high definition monitors in the market. It is important that you get a card that will let a user connect to as many monitors as realistically possible.
The best graphics cards in the market currently have additional features like a Fan /Vapor Chamber fitted cooler that is used to cool the card and avoid instances of overheating; most cards only have a fan and not a vapor chamber though. This has been necessitated by the increased functionality that the latest graphic cards are now capable of performing.