How can I run an additional electrical circuit to a wall mounted TV?
See my previous answer to a similar question.  (It's kind of funny.  I even mention that that same kit you found seems a bit pricey.)

I used a single, recessed, dual-voltage wall plate that lets you do your media and power cables all in one plate.  You just buy an "old work" electrical box, wire it up, and attach it to this plate instead of to the drywall.



I used 6-port keystone plates for the media ports, so I could put just the ports that I wanted back there, and even customize it easily later, if needed.