Install that last optical link and if you must insist on ARC, be sure to call Samsung and ask if it works.
Most of the time it does not work except for stereo. The reasons are well known but as it upsets most I don't write about it.
I've just purchased the LED 6600 model and a Denon AVR 591 receiver but can't get the TV audio through the AMP. Both devices support ARC.