Castle Creations motor and ESC combo recommendations for the HPI Sport 3 Creator Edition:

Sidewinder 4 w/1406-4600kv - 27T Pinion / 75T Spur  on 2s = ~30MPH
Copperhead 10 w/1406-5700kv - 29T Pinion / 75T Spur  on 2s = ~40MPH
Cobra 10 w/1410-3800kv - 33T Pinion / 66T Spur on 3s = ~50MPH

Note: All speed estimates are with stock tire diameter, high quality batteries and appropriately sized battery connectors.
Always monitor ESC, motor and battery temperatures on new setups or when changing gearing or batteries.