Castle Creations motor and ESC combo recommendations for the Hobao 8SCe:

Monster X w/1515-2200kv - 13t pinion / 40t spur on 4s = ~44MPH
Cobra 8 w/1515-2200kv - 11t pinion / 40t spur on 6s = ~56MPH

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.