Hey Shane,
Welcome aboard.
Let's start with the maps because that's the most important part of the equation. Are you satisfied with the maps you are using on the 60Csx right now? Satisfied enough that another Garmin solution using the same maps would do the job for you?
If so, you have two options. Some of your Aussie pals are using Garmin's old nRoute nav program. If you already have the maps in Mapsource on your PC you just install nRoute, connect a GPS receiver and head for the outback. nRoute will use any maps that are installed in Mapsource.
There are some downsides. nRoute is an older program that Garmin no longer supports so what you get is what you get. It has the same interface as Mapsource. Some of us like that. Some prefer the look of, say, the Nuvi interface.
nRoute also only works with older format maps ... the format that works with Mapsource 6.13.7 and older. That would be maps older than the City Navigator 2010 series (North America, Europe, etc) and onward, as well as older than their new Topo products (Canada, US, etc.). This is not a showstopper for those who like nRoute. There is a simple to use program called MapReverseConverter that will convert the newer format maps back to the old format and they'll work great with nRoute.
That's the free option.
Some of your mates are also using a new, not free, product that Garmin is currently selling and supporting. It's called Mobile PC. It's just like you stuffed a Nuvi into your PC. It works with the new format maps (and older format) so you can get new Garmin maps for it.
The one thing you need to be aware of is the difference between the two types of packaging. One package (sometimes refered to as the "deluxe version" or "deluxe bundle") contains Mobile PC, preloaded maps of either North America or Europe and a GPS receiver, either a GPS20x USB device or a GPS10x Bluetooth device.
These packages will only work with the GPS recievers that come bundled with them and won't work with any other receiver. The benefit of these bundles is that you can buy alternative locked map products from Garmin and other map vendors because there is a Garmin GPS receiver to unlock the maps to.
The other package is the "software-only" version. It also comes bundled with either Europe or North America maps but no GPS receiver. It will work with any NMEA-compliant GPS receiver from any manufacturer.
The downside of this package is that the bundled maps are locked to your PC at installation time. You can't move it to another computer for at least 6 months and you can't add locked map products to it because there is no Garmin GPS receiver to unlock them to.
I hope that all makes sense. If I've managed to confuse you just ask all your questions. Ask all you want ... I'm outa here for a vacation right away so someone else can answer them!!
Did I mention, welcome aboard and we try to keep things light around here?
...ken...