I just purchased a 2008 A4 and I would like to upgrade the Symphony Stereo to an OEM NAVI/DVD? Ideally, I want a unit that can plug in to and leverage the steering wheel controls and other features. I've seem to find many online; however, I really want one that connects to the existing GPS receiver as I want to avoid having any aftermarket receiver mounted on the dash.

Can anyone recommend a unit that can connect directly in to the factor GPS receiver? Make/model would be great?

Thanks in advance.