Does anyone here know for sure if you loose the 5th seat when ordering the Rear Entertainment option.

No, you are not losing the 5th seat.
Obviously, the middle rear seat is not that big but still usable.

Just to be clear, if somebody is seating in the middle rear seat, there is no way to control the rear entert. system since is located in the middle arm rest which will need to go up in order to use the middle seat.

Thanks for the info. I just wanted to make sure that the armrest wasn't fixed.