I'm interested in building a six to twelve monitor system that can display text and graphics either on independent monitors or spanned across all of them. what special hardware or software will I need?

I'm currently putting a project together for a gallery in which I will be building a six to twelve monitor display system capable of showing independent graphics/video and text on the individual monitors or allowing all monitors to span one single source. I'd like to know the best software and hardware solutions that will allow either independent or Spanned control of these multiple monitors. For example, I'd like to have the monitors sit side by side with text running from one end to the other, or switching to a system where each monitor has its own source. I'm open to using whichever operating system works best, as the host computer has not yet been purchased. Thanks in advance for your apples of wisdom, niko.