If you have a smartphone, especially an Android, use the stock Google nav system and a windsheld mount. You can enter or search for you destination with just your voice, the maps are always up to date, their's free traffic info, and you can still use it while on the move. I used to have a Garmin system that I loved, but gave it up because the my smartphone is better.
Regarding an aftermarket headunit, most are OK, but personally, I think the ones that use the Garmin software are the easiest to use.