have one question about the rand 7710. Can you download your own custom routes to it. all the Garmin's do, this is a feature I use all the time I prefer doing my own routeing.
There is a Rand McNally Forum over on POI Factory. It is not very active but someone there will definitely be able to tell you how to do this - if it can be done. Come back and share what you learn!
You will have to register with that site to post on the forum. It is a great site for information and free POIs for most GPS units.