If you listen to the Nomad spindle when it is cutting, it doesn't maintain very good velocity control except under light loads. The fact that it is only 0.07 hp (about 50 Watts) means it just can't do much.
A 500 W spindle (10x the power of the stock Nomad spindle) will barely change speed at the very small max load that the Nomad stock spindle can handle. But, it will allow cutting 5-10x faster in most materials. When cutting wood and plastics, slowing of the cutter by 10% or even more won't make any difference. Not having closed loop velocity control isn't optimum but its a great trade considering cutting speeds will increase 5-10x.
This spindle power supply has an input so that the speed can be controlled closed loop. A small magnet on the rotor and a hall sensor coupled with a cheap Arduino controller would offer closed loop velocity control with this system. In most cases I don't think its needed.
I should be able to post a video of the dramatic difference in cutting power within the next few days.