When you used it out bush, were you using that oztopo map? Or just what it came with?
The base map that is supplied with the Garmin GPSMAP 60CSX is not of any real use .... and the unit I had was imported direct from USA so the base map was for USA only !! - no good for Australia anyway.
I have used OZtopo which I found to be pretty good (a newer version is due out later this month).
I would suggest maybe starting with the "free" topo maps (for Garmin units) as suggested by "stfish" in this thread, to see if any are in your area (Alice Springs?) then trying those and maybe progressing from there.