I don't know if any of those system's video can drive the extreme resolution necessary for one of these, but a Matrox TripleHead2Go might work. You'd need to adapt to VGA, but it accepts VGA as the input from computer.

Or if you use the internal display as one, the DualHead2Go would work to add two more. (And it's more likely the onboard video on a 3400c would support that.)