"2-channel mono"
Er... that's as reasonable a definition of Stereo as I can come up with!
"less sound quality" as a result of being "only 2ch mono" is unadulterated balderdash.
I have the iPod -which charges, controls and sends signal and control data to and from the iPod. -I also have the aux input (currently temporarily mounted on an in-line 3.5mm socket, since I'm waiting for the real OEM part to be delivered) which allows me to squirt in an additional signal from an HD radio tuner. You could also use it for game audio from a playstation/sound from a portable DVD player/zune or other aftermarket mp3 player... anything that is external to the available audio sources to the car, which you'd like to hear through the speakers.
Keith