I was going to suggest you also look at the Vista Hcx unit. It is smaller and less expensive and I know several people who happily use this model. It also has a smaller screen and dual function buttons.
If you purchase Mapsource TOPO which has 1:100000 maps or Topo 1:24000 national parks central you will get all you need to lay the track over the map. The first covers the entire US but at reduced resolution. The second covers only national parks or forests in the central US. There will be a state wide version for Texas, 1:24000 scale, out sooner or later.
The maps can get a bit busy on the small Vista screen, but with a little practice you can use them to good advantage. Also, the points of interest data base that is included can be very helpful.
You can also use National Geographic Explorer TOPO for Texas, but you cannot load maps into your GPS with that one. You can plot tracks and make .jpg maps.
Take care you do not get hooked by the GPS bug.
