I went to Dux College for about a term and a half. All I can say about it is that (my tutor, at least) was fairly boring and was a waste of time (and money).
On the other hand is Talent 100, I have only heard good things about them. My friend handed in her notes to get them checked and Talent 100 thought she was having an assessment/exam that week and they delivered it to her doorstep by hand...at 1AM. I didn't even mention that she lives near Blacktown and went to the Epping branch (long distance). The down-side is that they are rather expensive at around $6000/year for weekly 3 hour lessons (extra 3 hour private classes are offered if necessary for no extra cost IIRC).
No idea about Intuition.