Definately do Monash (not Melbourne) enhancement maths.
I did it last year. It requires almost no effort.
Throughout the year we did no work at all, apart from assignments (which you can work on together as a class).
For the exam, all you need to do is create a notebook with a worked example of every type of question.
In the exam you can bring in as many notes and books as you want. So when ever you see a question, you just refer to your notes and use the example as a template for solving this. You can just refer to the monash notes if you want, but they are the most un-user friendly notes that i have ever seen. Its better to copy examples your teacher uses if you do it in your school.
Secondly you MUST get past exams, and do at least 1 one of them, (preferably the most recent.) either find solutions to it, or compare with other n then correct it. Bring those past exams into the exam. They reuse SO MUCH of the previous material in the current exam its unbelievable. 40% of the 2010 semester 1 exam, was a word for word, number for number copy as the 2009 exam 1.
It DOES help directly with spec. the vectors you do are much more complex than the spec vectors (don't stress there still not hard), and then the vectors in spec just seem like a joke. You also learn many shortcuts and tricks that you can apply in spec, and if you happen to find such a question, you could solve a 4-mark, in a few lines.
THe biggest bludge subject, so it allows you to spend much more time on other subjectts, while still getting a great mark.
as i said i did no work throughout the entire year, apart from completing assigments.
i only spent 1, maybe 2 days b4 each exam, preparing. all i did was complete about 2-3 exams, n chek answers. that is all the revising u need to do.
to get a 5.5 u need an 80% average. everyone in enhancement get s above 80% easy, as far as i no, at least in my school.
Most of the class got above 95%, for both exams.
I got 100% for the 1st, 99% for the 2nd semester. I was the awarded the Monash Prize for the highest achiever for that subject (beating both uni n enhancement students).
Do uni (monash) maths if u can.
Cheers,
Nikhil.