the motors u get with the mamba kit are just cheap chinese imports distributed from the USA at blown up prices. Hacker motors, however, make the best brushless motors in the world (then again, their german). u would know this if you fly rc planes and helicopters. i can guarantee that the hacker motor runs more efficiently than ur 5400kv, and easily puts out more torque. the speed can be compensated for in the gearing. if ur going to run a 3s lipo setup, ur going to start to get heating issues with a high kv setup, and the motor is going to struggle on the amp draw. the hacke e30 was designed for 3s lipo use. my mamba heated up hardcore on 3s and that was with a 5000kv motor. what u have to understand is that, a motor with 5400kv 70% eff, is equivalent to a motor that is 4200kv with 90% efficiency. that is because u get more voltage drop across the motor with decreased efficiency. u wont admire the hacker setup unless u own one. this is just my 0.02c.