Answer regarding the Maps only.
SSA is old style maps but very good for routing. (Map detail is very good in Africa)
The Data is bought by Garmap which is now Garmin South Africa from TeleAtlas which is owned by TomTom
Unfortunately they cannot compile the map to emulate City Navigator which is Navteq Data, Garmin makes the firmware of the units specially for Navteq (CN Maps).
Tracks for Africa is another option which is very good for 4x4 Adventures (off road stuff we love in Africa)
T4A is not too good for the City but for the Great Outddor it's good. (Also no enhanced features, even the address search is not so hot.)
People generally use Garmap to get to the location and then use T4A for the Adventures (very good POI)
In order to get all the enhanced features you need City Navigator Maps.
On Another OT
Did you buy your Garmin in Africa ? Which country ?
I've been looking for the gmapdem.img for the South African Region for a while.
Regarding your Question about 3490 vs 3790
You need to look up the features of each print out and compare.
This, my friend is so very useful. I actually bought my 3790 from the U.S. So, is it possible for one to lay hands on the SSA City Navigator Version that contains all the good and enhanced features, if yes, where, PLEASE. I really appreciate you help. And one more thing, sorry for the delay in reply, was out of ACTION for some time.