Hi Marco,
I certainly understand you not wanting to get lost! I don't have any experience with aftermarket GPS/NAV systems. The ones that I have seen as OEM in various makes/models work but are a huge distraction. I would try and find one that offers regular updates to streets and such. The best system is only as good as the mapmaker. If the map info is outdated you are SOL. Whichever you choose I hope they give better directions than Yahoo maps!

Lee