Definitely go the microstepper route, lower motor resonance and smoother performance.
Try this, 3amps and up to 55volts. The nice thing is it is a microstepping chopper driver board. Software is open source and the design works great. Very smooth at 8 microsteps.
http://www.embeddedtronics.com/microstep.html
Kin Fong
http://www.embeddedtronics.com