Ha, when I lived in Brisbane I worked at a tree farm! Poinciana's were very popular, as were Jacaranda's, they are not much more messy than a Poinciana tbh. Also Leopard trees were good sellers too cant remember the bot name... Lagerstroemia's are a nice tree, though they arent massive. Also Liquid Ambers are very pretty though they do loose their leaves. I'm probably not allowed to link the tree farm on here, but I remember when I was there they had a collection of random advanced trees that were ends of rows or returns.... It would cost you about $1000-$1500 for a 3-4 meter tree, thats freight too as they weigh lots.... its worth it though if you have the money for instant shade and less years nurturing a baby and waiting for it to grow. PM me if you want the details or any other info.