Thank You, appreciate you taking the time with a newb. 
I was mistakenly under the impression that all the Nuvi's shared the same design (other than the City Nav differences, bluechip etc) with the exception of the 500. Where they would all be the same with the addition of Mapsource and Topo.
I now see the models you mention allowing the routes being the difference.

I was mistakenly under the impression that all the Nuvi's shared the same design (other than the City Nav differences, bluechip etc) with the exception of the 500. Where they would all be the same with the addition of Mapsource and Topo.
I now see the models you mention allowing the routes being the difference.