I bought the Power Acoustik DVD headrests for my 2011 EL Limited. I paid Best Buy $200 to install both. When the tech was quoting me install before my purchase, he said $200/side. He seemed to think that was too high, so we spoke to the store manager, who agreed that $200 total was fair.
They seem to work all right. My main complaint is that they rattle compared to the factory headrests, and there is almost no head support, especially compared to the huge factory rests.
We had an 07 and still have a 2010 with factory DVD. The Ford headphones do not work with the aftermarket unit.