What's the best way to determine the actual capacity of a controller? What component(s) limit the total wattage? I have a mill with the following controller:

LittleMachineShop.com - Motor Controller, 3900 Mini Mill & 4100 Mini Lathe

Spindle Motor sticker says 500W, 230V 2.8A.

I was wondering if it's possible to replace some of the components on the controller to support a larger motor, possibly 1100W or more. There are (6) IGBT on those heatsinks (ST GP7NC60HD). The controller is wired on 120VAC input but I believe it will also accept 240VAC.