Most people here use systems with a software controller capable of handling multiple simultaneous axis moves. For example, use Mach2 ( http://www.artofcnc.ca ) , load in your g-code file, and Mach2 will output step and direction signals for up to 6 axis of movement. Each motor has a driver, one example of which would be the Gecko ( http://www.geckodrive.com ) which takes these step and direction signals and supplies current to the motors. To use your single axis controller, you'd need software to interpret the g-code, do the interpolation, and send that info to each controller. I doubt if this software exists.
The easiest thing to do would be to use either Mach2 or TurboCNC, and get some drivers that take step and direction signals to run your motors. Any other way is much more complicated, and you'd be pretty much on your own, in my opinion.