First off, is the basement finished below the entertainment center & do the phone wires come into the basement? or do the phone wires come into the attic and do you have access to that area?
Next, do you want to fish wires through the wall & install a jack?
My phone line comes into the basement. There is a terminal strip with terminals for attaching inside phone lines. I would run a new line over to where the entertainment center is, drill a small hole in the floor & run wires right to the equipment. However, fire codes may specify using a jack? Then you got to cut a hole in the wall and fish wires to it.
Telephones use 2-wire lines. Wire all inside extensions in parallel off of the terminal block.