I would definitely get one in the 1->2 amp range..
I setup a weather station with an xM C, with just a usb camera and
wifi, under load (picture/compression/upload) my xM is pushing
650->750mA, before it drops down...
Digital electronics tend to draw power in bursts; a cheap PSU might be
able to keep up with the average current demand, but not the peak
current demand.