if you can drive the displays with a video card there's the option of a PC with three video cards. I guess the monitors have three BNC? (RGB, sync on green). try getting one hooked and working, with a VGA to BNC cable. Powerstrip on windows, or modelines in Linux may be needed, and probably some hardware circuitry, try do do some search on that topic. Obviously the first, road-blocking step.
The PC could have a motherboard with at least three PCIe 16x slots (AMD 790FX, nforce 780a, 680i, or Intel P45 chipset. that's a bit expensive), a cheap CPU and three geforce 8400GS. you can also stuff an older motherboard with PCI cards, for instance a PC with a dual head AGP or PCIe card and four single VGA PCI cards would do it.
Linux is suited to make such a display wall, try finding out about such setups. Again, not the easiest thing on earth.
the PC then can plays DVD or media files on its own, or you could stream content from another PC with vlc or something.