All high-end graphics cards have multiple monitor options. If you want three monitors, get 2 cheap cards, like a radeon HD2400, and you'll have 3 monitor connectivity. Buy a Radeon HD5850-5870 and you will have 3 monitor support from that single card. (6 if you buy two)
Buy a GTX570 and you'll have 2 monitor support, and an enthusiast gaming graphics card, wasting 300 dollars you don't have to.