Have you looked into a BB 400 like the Multiplex Permax 400 BB Motor located at http://www.hobbypeople.net/prdcls/motorac02.asp ? I don't know the specs on this moter but Watt Age also has a BB 400 Cobalt motor that claims peak efficiency at 18 amps so I bet it would work with 3 Li-Po cells. My understanding is that these motors use regular controllers and cost between $35 and $50.