yeh. The bigger motors require more watts of power. And therefore you need to get transistors that can handle the larger voltage and currents. These can get very hot and so you need heat sinks to cool them.
The circuit doesnt need to be much more complicated i dont think, but the circuit will get bigger in the way that the tracks on a PCB will need to be thicker for the current, more heatsinks and the the high current components are bigger.
The circuit may get more complicated when needing to isolate the huge power supply from the on board electronics like microcontrollers and such.