Yep N.T. is a must do. I have been lucky enough to travel all around Australia, but Litchfield & Kakadu National Park stand out. Both in the dry and the wet. Rains so hard, windscreen wipers don't work.
Contrary to what you hear, Darwinites drink more iced coffee Moove than beer.
South coast is my gem. I'm glad you like Narooma. It's a peach. The missus's ma lives there and she goes to Montague island to assist in the upkeep. I'm there fishing off Dalmeny catching salmon as often as I can.
I like your idea of a mass Pentax meetup for the Sydney people, but it would be hard to arrange all at once.
Thanks
Peter