Hello Zeal.
The Wave Mechanic (at least the model which I have) is a high quality power filtration device. NAS takes the position that filtration of line power makes an improvement in the sound, a position with which I concur. I would be hesitant to put a potentially noisy controller in front of the motor, so, absent a trial in your system, I would stay with power filtration.
Wave Mechanic as overkill? It depends on your POV. I used to run my NAS Mentor/ Mechanic through a prior isolation transformer. When I added a CVT (constant voltage transformer), it SEEMED to improve further. So I use all three: a 500VA medical isolation transformer from Plitron, a 30VA CVT from Sola, and a Wave Mechanic.
One other argument for the Wave Mechanic is that, as a power filtration device, it protects the motor, which is a high value item.
Good luck!