Stick the cable through the back of the radios hole, as circled above, and down behind, then out below the ashtray. Route it around the shifter. Be careful it doesn't get mixed up in the workings of the e-brake. Pop out the little plastic 'door' at the front of your drink holders, and run the wire through that.
If you want, you can use a Dremel or similar tool to grind a small hold in the little plastic cover, than you can slide it back on with room for the audio cable to come through.