RE: B400 Replacement Motor
The scorpion motor has all the power you could ever need/want. I think it is in the $54 range, but there is no way the stock ESC could handle that motor, so you would need their 40A ESC. I think that is in the $60 range. Or you could get another ESC around the 40A+ range. I have seen them at Helidirect and Readyheli.
Nick