Regarding SW WA - there's Margaret River, Yallingup, Augusta, Pemberton, Denmark, Albany, etc. All worth several days, so time probably an issue if you're only in the area for a week. I have three or four trip reports for SW WA posted here on Fodor's if you want more info. Just click on my name, then look at my trip reports - warning - they're long and detailed.

Thanks to everyone for your valuable feedback. I've decided to spend a week in Darwin/Kakadu and a week in Perth/SW Australia. Momentarily I'm going to post my tentative itinerary for Darwin/Kakadu in a separate thread and would appreciate your comments. I'll post something on Perth/SW Australia later.