I have several GPS devices. One of which I have for the car is the StreetPilot. The screen is very similar to the Nuvi. This would be a poor choice for touring IMHO. It just does not show you the detail that my 76CS does. I prefer the 76 over the vista, the screen is just a little bigger but you still might have problems seeing the display.
I like the stick on bifocals idea.