I do not think that it makes much sense to design your own motor driver board, there is more to it than a plain power driver. You also need current regulation for two phases and - if you do not want to run your motor in full step mode, as I presume - intelligent control circuitry to set the phase currents.
We are using driver subsystems from IMS
They manufacture drivers in different form factors (with pin connectors, screw terminals etc) which can easily be integrated on your own pc boards as well as on panel boards. They interface easily with NI cards.
http://www.imshome.com/index.html
http://www.imshome.com/products/discrete_drivers.html