The load on the motor is what defines what the motor needs power-wise, not the motor itself. The Ace ESC will drive the HK2221-8 without a problem. I switched it for a Castle Phoenix 35, but that was just because the governor in the Ace ESC wasn't all that. It works fine with throttle curves, though, and with the 2221-8 on 3S packs you shouldn't push over about 30A or 300W unless you're seriously slamming it around.