I would go with the HAF 922 Case
the samsung or a Seagate Barrcuda 7200.12
if you uped your budget a little you could get a blu ray combo from Samsung for $89 AUD
the 550watt psu
i'd go for g.skill ripjaws 4gb ddr3
even though i am a ATi fanboi id go with the nvidia EVGA 450 w/ the civ 5
the GA 880GA-UD3H will be prefect
for a little more i would get the AMD Phenom II x4 965 for just a little more you get 500mhz more and unlocked cores.