Well for maths units you don't really have a choice in terms of what you study (you could choose the stream, but you basically cover the same topics). For science, especially if you are interested in the neuroscience aspect of psychology, I'd definitely recommend taking units from the neuroscience major (you could possibly complete a minor or second major if you wish).
So with that in mind, and given your background in the HSC, I'd recommend the following units for your first year:
Semester 1
MATH1011 - Applications of Calculus
MATH1015 - Biostatistics
BIOL1001/1911 - Concepts in Biology (Regular or Advanced)
CHEM1001 - Fundamentals of Chemistry 1A
PSYC1001 - Psychology 1001
Semester 2
MATH1013 - Mathematical Modelling
MATH1014 - Introduction to Linear Algebra
CHEM1002 - Fundamentals of Chemistry 1B
MBLG1001/1901 - Molecular Biology and Genetics (Regular or Advanced)
PSYC1002 - Psychology 1002