I saw an OEM radio on ebaymotors starting bid $10, do you guys think the phone input is a mono sound or is it stereo and adjustable?

I might be better off picking up a Cayanne radio with optical ports or else get the Crossfire nav radio.

edit:
this might have answered my question on the phone input, http://www.siocommunications.co.uk/06-108B.html though you still might be able to tap into the rear speakers with a little custom wiring.