Since you asked, I'm going to answer, knowing totally it's not what you wanted to hear. But this is what I use.
I have an old school Lowrance Expedition C handheld. I think more of it than Starfleet thinks of Tri-corders, in vehicle and out, on road or off, I always know where I'm at. Heck it even has a barometer. I use it in the vehicle to navigate highways to this day, even though it has no auto route capability. It's seen Nashville's interstates all the way to hiking in thickets, to being strapped to the dash of a kayak. I say old school, but this was top of the line only a few years ago, before "mobile devices" took off ridiculously as the jack of all trades master of none devices. While most people were dropping their phones and fancy tablets in the creek once and having to replace them, I was using my handheld in the rain, face planting it in the dirt, dropping it on rocks, and mashing it on my backpack for years, and I'm still using it every time I leave the region of Earth I know like the back of my hand. I doesn't loose signal in the trees, doesn't complain about no connection to load maps, and sure as heck never rings when someone thinks they are going to bug me while I am busy exploring.
Sadly though, I will probably watch this thread with interest, as I too probably need to upgrade to a tablet for in vehicle navigation. My netbook never was that great in the vehicle, and I ultimately stuck with the handheld for 90% of trips since it was click it in the suction mount and go. The netbook is a pain with cables and mounts.
For mapping software, a little time on Google earth to mentally familiarize myself with the area was usually enough to find a path, but not always efficient. As far as interfacing with GPS, I ran MapPoint 2006, a really high end corporate version of Streets and Trips I found cheap. I also ran a number of other now obsolete programs, that don't do me much good today.