Castle Creations motor and ESC combo recommendations for the Traxxas XO-1.

Monster X 8s w/1717-1650kv - Stock gearing (14/46) on 6s = ~50MPH
Monster X 8s w/1717-1650kv - Stock gearing (14/46) on 8s = ~65MPH

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.