Giving a clue to the country you want it for might help!

I'm in the UK, use a Navman 520 and find it very effective for most of the time. The biggest problem is that in cities there are constant changes to the road networks as new one-way systems are introduced, etc, and naturally these are not on the map as delivered. With Navman, the sites selling compatable maps only say things like "the CD contains latest version of the UK map" and don't give the slightest hint on when they were last revised. I can't even tell if they are newer than my 2+ year-old maps.