It really depend on the motors you're going to use. Gecko's can supply up to 7A @ up to 80V, while the EAS can only supply up to 3A @ up to 55V. You want to supply as high a voltage as possible for best performance, up to about 20x the motors rated voltage. This will give you the most torque at the highest speeds.
An alternative driver, that is used by a lot of people here, is the Xylotex board.
http://www.xylotex.com
While only 2.5A and up to around 30V (It's rated at 35, but recommended to be run @ 24V to 30V,) It's the best deal around for only $125 fully assembled. For another $60, he'll give you 3 motors to get you up and running for $200. For a small first machine, this may be all you need. Get the Gecko's for you're second, bigger, faster machine.
Gerry