an anyone tell me how the 16687006969116, (which is Identical to factory-fitted optional extra "Rear Seat Entertainment System" Code 864) wires in vs. the much less expensive 1668700796 Accessory Rear-Seat Entertainment System wires in?

Both systems say they require the 866 RSES pre-wiring kit, (although I had a M-B salesman tell me that all GL's are pre-wired and you don't really need the 866 option in order to add Rear Ent.)

I was quoted $2500 for the 16687006969116 by my dealer who said you must also add the appropriate headrests & covers, another $1100 before the vehicle will accept the DVD Screens included with this kit.

Whereas the much - MUCH less expensive 1668700796 Acc kit is ready to rock with everything it comes with.

I'm just curious where the difference lays when it comes to wiring them both.

Appearance-wise the 16687006969116 is built into the headrests, whereas the 1668700796 seems to hang off of the headrest supports /mounts underneath the headrests...but how do they wire into the factory system?