Whaler's Cove in the middle of Dunsborough. Right on the beach, nice units, we usually pay $1000 for 5 nights and get 2 free at this time of year. (I think it's 3+1 for $600 too, but you'd have to check.)
http://www.whalerscove.net/
You'd want the smaller 2-bedroom units like Pioneer, William Tell etc.