Personally, I think getting another 4 in 1 is a waste of cash when you consider you can buy a 3 in 1 AND reciever for only 90 bucks. Throw a BH head on there and use lipos and you have yourself a CP Pro.

Unless you plan on flying aerobatics then you can use your own transmitter.Only difference in the transmitters is the knobs on top that control pitch curves in idle up mode.

AND you can now add a brushless motor and headlocking gyro plug and play. No fuss no muss just plug them in and youve got 1 bad*** machine.

Im actually going to the 3 in 1 setup in a couple weeks and going brushless. My Bday so everyones getting a list of parts lol
Now I know some guys will say why not just buy a CP Pro and sell your CP. Well, try find someone who will give you what you want for your CP now that the Pro is so cheap. Youll lose money for sure.
Of course this is all my own oppinion.