Has anyone used the auxiliary plug found in the RTLs with Navi? If so, how do you use it? Do you just push the CD/AUX button on the radio? What does the LCD display show when the auxiliary function is being used? The reason I am asking is I have the RTL w/SR and the button labels on my radio look exactly like the ones on the RTL w/Navi...except of course the navigation screen. I'm trying to see if I can add an aftermarket auxiliary adapter to the radio without losing any existing functions (i.e. AM/FM, CD changer and XM radio). Your input would be much appreciated.