Nate,
That was me on the the The Wire I've made several posts/replies and mentioned GeoCaching. I am an Isuzu fan, with my original 1993 Rodeo, although 2wd.
I have a Magellan Meridian Gold, with a 16 meg memory card, and upload regional maps from the Street CD. Although, from what everyone recommends my next purchase will be the Topo CD, people say it has all the standard roads plus topo maps.
I use my MeriGold in the Isuzu, hiking, and biking. I recommend you find a store that has Garmin and Megallans, look at them both and decide which you like better. Both make quality units. I have had excellent success with my Magellan Meridian Gold.
Just about any unit would be good for hiking, 4 wheeling, fishing, or just getting out in the woods. Just remember to mark a waypoint of your car or starting point of the trail (or boat ramp), then you will be able to find your way back easily.
-Robert
-MeriGold and Isuzu owner.