ASK HN: Quad monitors - advice? tips? tricks?
alex_c: I've never used more than two monitors, but I know most people who run three monitors use two (usually mismatched) cards.  I don't know of any four-display video cards - I've never needed one - but if they're a lot more expensive than two off-the-shelf video cards, I don't see any reason not to go for the cheaper option.