I'd recommend flying the stock motor and seeing how you like it before spending extra money on a brushless power setup. The GWS IPS motor and gearbox setup that comes included is quite robust and flies the Pico Moth quite well indoors. I flew mine with the GWS ESC300 LiPo compatible speed controller and it was terrific right out of the box.

The one thing you will want to do is to replace or reinforce the stock wing struts. The plastic struts included with the kit are flimsy and cutting new ones from 1/16th balsa sheeting or reinforcing the plastic struts with 1mm carbon will go a long way toward helping prevent your wings from folding.

Other than this one weakness, the Pico Tiger Moth is a fun kit to build and a really enjoyable airplane for indoor slow flight.