Is a multiple-output video card REQUIRED for running extended desktop?

I already have a single-output card. Can I just simply hog another PCI slot with another single-output video card and run a multiple-monitor desktop that way? Or is this multiple-output card type that I keep seeing everywhere required to do such a thing?|||you can use another single output card, but you must connect the two cards together with SLI so basically they act like one, you have to have SLI compatible cards though