I have the 60 series hcx and have the 2 gig card in it. Don't have any topo's yet but i installed the CONUS road map with all of the points of interest and that used almost 1 gig on the card. So there is plenty of room for more stuff on the card.

Have been impressed with the level of detail in the road maps, yes there will always be some errors but this past weekend i went out to a friends property that is out in the sticks. The "road" to the property was two tire ruts and when the GPS pointed to turn here it was right in front of the pasture gate. Still can't believe that i drove my rice rocket though a cow pasture.