See the following picture for the entertainment center in question:
It was originally designed for 4x3 Standard Definition TVs to be placed in the bottom left alcove (partially hidden by the Corona--sorry, this was the best picture I could find for illustration). As a result, all of the cable hookups are in that alcove instead of up on top.
I'm not concerned in particular with drilling a sufficiently-large hole through so that I can run power and coax/Ethernet. I'm particularly interested in finding the correct pipe/tube that I can run through the hole, and then the necessary finishing parts that I can hook on each end to make it look like it was supposed to be there to begin with.
I'm planning on building a shelf to go in the lower left that will house a new surround sound receiver, xbox 1, and HTPC (the latter both pictured), so I'm considering something around 2 inches in diameter. Thank you for any input you can provide!