The whiteAnt will work with a 6 amp 12 volt power supply. If you add more peripherals to the machine, like heating bed, you will want higher current. Each motor draws 3.0 amps at full torque. Most of the time, only the x and y axes are moving at the same time, and the drivers are only allowing a max of 2.5 amps and they should be set for about 2.0 amps so they don't overheat (they have overheat protection and the LED will light up, so you will be fine if it does overheat, but your model may suffer). The remaining current will be enough to keep the hot end heated.
Click the link to add information to this solution:
What power supply would be adequate for the whiteAnt 3D printer?