You almost certainly have optical audio. If this is the case, you cannot just replace the stereo and must replace the entire system, stereo all the way to speakers. If you have HK audio or Bose (not sure which was available on the 2007) then you absolutely have optical audio. If there is an amp in the rear quarter panel with two optical fibers going to it, or if you pull the stereo and it has no speaker wires (purple, gray, green, white) then you absolutely have optical audio. This means your cheapest/easiest option is going to be fixing the OEM setup.