Crossfire and SLI basically allow you to connect and use multiple graphics cards in a single pc, in order to improve graphics performance. While this sounds good on paper, in reality it is highly dependent on the game developers adding the support for these technologies in their games, which they rarely do. If there is no support for SLI/Crossfire in a game, no scaling will occur and the game will work as it would on just one GPU. Even when there is support, microstuttering is a common and highly irritating occurrence. In addition, multi-gpu configurations often waste more power and produce more heat than single higher end graphics cards, while having overall worse performance in most games. TL;DR : buy single high end graphics card rather than using multiple lower end ones in multi gpu configs
