The next bit is something to consider very carefully if you want an extreme gaming PC. This is the graphics card. This is the most important bit if you want to play the latest games at the highest settings. There is no use getting a very fast overclocked CPU with lots of RAM in a fancy case etc, unless you have a very good graphics card to go with it.
While an office PC can get away with onboard graphics, an extreme gaming computer, the graphics card has to be very high end. In fact, the most powerful gaming computers have 2 or 3 of the highest end graphics cards running in tandem in SLI or Crossfire mode.
There are only two major manufacturers of graphics cards at the moment; AMD and NVIDIA. Each one has its fans but truth be told at the high end there is not much difference in performance in most games whether you choose AMD or NVIDIA. What blurs the lines further is that updated drivers are released by both manufacturers regularly and drivers can make quite a significant difference in the performance of the graphics card. So the fastest card this week might be from NVIDIA and with a driver update AMD might take the title the next week and it might revert back to NVIDIA the week after. In terms of value for money, AMD cards usually tend to provide more bang for the buck.
The only way to get faster performance from the highest end graphics cards is to use them two or three of them together in SLI or Crossfire mode. SLI mode is when two or more NVIDIA cards are used together. Crossfire mode is when two or more AMD cards are used together. Remember SLI or Crossfire is only useful for gaming and will only work if the game you are playing offers SLI or Crossfire support. With either option, while the first or primary graphics card will offer 100% output, the second graphics card will at most offer around 80% (usually only 30 – 50%) performance boost. A third graphics will only offer a further 20 – 40% performance boost. How much of a boost depends on the motherboard used and the game being played. What this means is that with 2 graphics cards in SLI or Crossfire mode you will get only a maximum of 180% the performance of a single card and with 3 you will get at most around 220% the performance of a single card. Usually the gain will be much lower.
Most motherboards run the first card from a 16x PCI-E express slot and the second from 8x PCI-E slot and don’t offer support for a third graphics card. The best motherboards will offer support for 2 graphics cards via 16x PCI-E slots and the third and fourth card will be supported via 8x PCI-E slots. 8x and 16x PCI Express slots basically refers to the width of the communication pathway between the graphics card slot and the CPU, so an 8x PCI-E slot can at most offer only half the speed of a 16x PCI-E slot. So if the motherboard you choose supports one card at 16x and another at 8x the most you can hope for with a second graphics card is a 50% but realistically it will be between 0 and 30 – 40% depending on the game you are playing.
Keeping mind all of the above
Keep in mind that to run SLI or Crossfire, you will need a bigger power supply, a bigger case with more cooling and a motherboard which supports SLI or Crossfire (which obviously will cost more money). Considering the added expense that comes with an SLI or Crossfire setup and marginal improvement from adding a second card, in almost all circumstances it is better to get one high end gaming card rather than run 2 mid-range cards in SLI or Crossfire mode. The only logical time to go for a SLI or Crossfire setup, is when you have already gotten the best possible graphics card available and want to improve the performance even further and the budget is not an issue.