Sydney to Perth driving

Just a couple of questions that will help us answer you.

Why and what are you looking for?

Also on you and the vehicle:
What type of car and caravan etc? Are you interested in dirt roads that may be corrugated or do you just want to stick to the bitumen etc.

Any outback or remote travel experience?

Enough to see on that road for several trips do a bit of research you may feel as i do that it is worth the extra trips. Apart from that there is the "longest shortcut" dirt for a lot of it but usually in good condition.

The train is expensive for vehicle movement, but consider the actual costs (fuel/food/accommodation) in driving and it's not out of the question. Driving the Nullarboring twice in that short a period isn't going to be exciting, I can assure you.

You did say that you have no outback driving experience - are you good for the long haul? More info here would help. How many in the vehicle? At least two drivers to rotate is pretty much essential on your timescale unless you plan a tumble-turn in Perth.

Is your ASX a 4WD or 2WD? If the former, that "longest shortcut" will give you a taste of the "other" Australia, and probably whet your appetite for more adventure. 2WD will do it but the loose sandy sections (such as near Docker River) can be trying for the inexperienced, and sticky sections can be an issue.

I'm not trying to deter you, far from it, but there are things to consider.

Going the shortest, fastest route, it is 40 hours driving time. I know because my dad and I drove back non stop once, one sleeping and the other driving in rotation and it took 40 hours. I don't recommend that, but even 10 hours a day in the saddle means 8 days driving out of the 12-14 days. I don't reckon you have time to go off onto the slower dirt roads through the centre.
If you want to vary the trip, go via Hay and Mildura to Port Augusta, then the main road through Norseman to Perth. Come back via the south coast towns of Albany and Esperance, back up to Norseman, then Port Augusta and home through Broken Hill and Dubbo. That's a hell of a lot of driving in 2 weeks. :-) Between Norseman and Port Augusta, you don't have any other tar road options.

Not overly familiar with attractions east of Port Augusta, but you could mix it up one way or the other by taking in the wonderful Eyre Peninsular.

Contrary to earlier commentary there are a myriad of attractions along the Nullarbor and the Nullarbor operators association and WA/SA tourist bureaux have a great map brochure which could tie you up for a week on the Nullarbor alone!

Bring a few golf clubs and balls and play the worlds longest golf course with holes between Ceduna and Kalgoorlie.

From Norseman, you can turn left and go down to Esperance and follow the magnificent rainbow coast to Perth taking in the forests and wineries of the southwest as you go.

Turning right takes you through Kalgoorlie with its great history and magnificent buildings and the unspoilt beauty of the Great Western Woodlands with its huge Salmon Gums and Gimlets, then follow the water pipe through the Wheatbelt which will be an absolute picture of green and gold and pink in September.

Choices choices choices - Enjoy!

Another option for the Norseman - Perth section is simply to go straight west of Norseman on the gravel to Hyden and Wave Rock then continue on west to Kondinin, Corrigin, Brookton and into Perth.

I came through there 8 weeks ago and the road was in good condition. Although there has been rain since I don't think this would cause much of a problem.