Just crawl under the seat. Hook a RCA to headphone plug to the AUX inputs on teh back.
Get a LONG one. You will thank me later.
You can then drill a hole in the glove box and pass the end through, or enlarge the drainage hole in the bottom of one of the cup holders and run it out there. Makes keeping it in the cup holder convenient, just dont' get it wet.
I just pulled a cup holder out, and ran a cord out temporarily, then crammed the cup holder back in when i needed an AUX on a friend's boat.