Darkfox1,
I understand your thoughts pretty well. Probably the only difference is that I could install the OEM NAV as an accessory (thank God!); I also found a place (just on the other side of the border with Switzerland) where I could save about 40% of the price of the original parts. This was what made me switch to the OEM solution.
For the MP3 I have an iPod, too, and the original AuxIn interface. I plan to verify what products Alpine and others are designing to integrate iPod with OEM systems (ie KCE-425i).
I'll do the FS post in a few days, anyway.