Let me add just one thing about brushless motors needing separate ESC's. Brushless motors can not be wired in series, but it is possible to wire two brushless motors in parallel to a single (suitable) controller. Not all brushless motors/ESC's work well this way, but it can be done. Kontronik controllers seem to work best for this task, using Kontronik or Aveox motors. Dedicated motor/ESC pairs are more goof-proof, but there are other options.

-David