Crossfire is ATI's take on the two-card set-up to boost graphics performance. Nvidia is a manufacturer/designer of chipsets, as is ATI, which has recently been bought by processor manufacturer AMD. Nvidia also has an iteration of dual-card set-ups called SLI. I don't think there's a great deal to choose between the two different chipsets but I'm sure enthusiasts will wander along with views on that. For the record, I have an SLI set-up which is great for gaming.