My main concern are the floods if I was to drive Alice to Katherine to Kununurra this time of year. Has anyone been caught out in these floods and would the trip from SYD to Kununurra still take 5 days?
If you take that route you'll be fine at least as far as Katherine. The Stuart Highway is completely open at the moment all the way to Darwin. Takes a fair bit of rain to knock it out. If you try and take the shorter route via QLD and the Barkly highway... well thats a different story. Its still closed as far as I know and will be for a little while yet as they try and find the missing bits and put it back together
I really hope your Sirion is the 4cyl 1.3L model and not the 3cyl 1.0L model.