Yeah G`Day Rob,,
DR650 are reliable old workhorses for sure 
As far as the GPS goes,, hard to go past Garmin 60CSX or the newer 62S for mid price range, great mapping and routing capabilities and tough as nails.
Or you can go the top end ZUMO or OREGON series which are more like the car units with Bluetooth etc ans wider screens.
However, the Zumo`s have not shown to be as reliable as the good old CSX`s for offroad and desert running :whistle:
They all run Aus/NZ TOPO maps real well or you can make do with free maps from “SHONKY MAPS” that run on the standard Garmin , depends on how much detail you need for trips you plan. Shonky is suprisingly detailed actually and a lot of guys use it on here as a backup for Aus Topo 
TB has them all :laugh: He is a GPS hoarder
He is out at Birdsville and beyond till next sunday, but will chime in with good advice on the units and mapping options when he gets back for sure 