I suspect that the Gecko recommendations are based on linear power supplies. The trouble with switch-mode supplies is that they can hard-limit at max current which gives stepper drivers a problem when they demand short but high-current pulses. Linear supplies with their big smoothing capacitors will handle this with no problem - it doesn't matter in this situation if the output voltage drops a few volts when you demand higher than rated current for a few milliseconds. If you are looking at cascading a switch-mode inverter off the back of a switch-mode power supply, it might not handle this kind of load very well. Linear supplies needed to be rated for average demand, switch-mode for peak demand, as a general guide.