1) i think that AXI motor is suitable for a hornet or maxir. the MX400 (x400) needs something that will fit in a Trex
2) HS60 servos??? i never heard of those. 4 qty HS56 will work very well
3) 20amp is too low for the x400 unless you get a frugle amp draw motor like the Neu 1105/3y i wouldnt use it. you should use a 25amp absolute minimum even that could be risky if you use a powerful motor.
4) 1350mAH is small for the x400. although i bet it is capable of lifting off the heli i dont think it should be used. x400 like the trex, use 1800-2200mAH lipos.
5) any 6ch Rx works.

i HIGHLY recommend the futaba GY240 or GY401. probably the 401 as it's just easier to adjust and doesnt cost much more. once you have a gyro like this you probably wont go back to anything else.