Hmmm that will really depend on your rock scape, the number of return pump, the flow of the return pump, the position of the wavemaker, the height of the tank and finally what are u keeping?
There is a lot of factors to consider, my tank is only 1.5ft height, my overflow is in the center, with 2 outlet to the left and right. My rock scape consider of minimal rock. Hence 2 wavemaker is enough for my full sps tank.