A rule of thumb when selecting power supply for steppers is to add up all the phase currents and multiply by 0.6
So for instance say your using three 5A steppers
3*5A = 15A
15A * 0.6 = 9A
So a 9A power supply would be the one you want to use. You never want to under rate a power supply though. If the closest you can get is 10A like the Keling KL- 5010, this is still okay.
Hope this helps...
~Scott