Running wire through built-in drywalled entertainment center
Not entirely sure what exactly you're looking for, but several companies make in wall runs for tv/speaker wires. Most just assume you will be running the cables in the wall itself, and provide either blank-canvas wall plates. Some provide end point connectors in order to provide a wire 'socket' for the wall plate.

Here's a video tutorial on a simple version of this. 

http://www.diypete.com/how-to-hide-tv-wires/