700-800 AUD$ right ? Well am sure if you want to have good gaming performance as well, then it would go a little over $800...
Here is a sample config -
i5 760 - $229
G-B P55-USB3 - ~$139
RAM - 4GB DDR3 GSKillz/ Team - ~$95
Graphics card - HD 5770 - $174
HDD - WD or Samsung or Seagate 500GB - $48
PSU - Antec ECO HCG 520 - $90
CASE - Antec 300 - $65
Total - ~$840
X4 955 + Asus M4A87TD-USB3
Rest same - This setup would cost ~$100 less...
what about a $100-ish graphics card? gaming isnt a priority really, i can cope with it as long as it can run Left for dead 1 or 2 (and similar) games on low-mid settings.
and as long as it has HDMI/DVI im good.
^ Then you can get a low powered card like HD 5750 or even HD 5670, but I see that you are fine with Mid-settings, then check out cards like HD 4850/ GTS 250/ HD 4870,...these are all very good cards and are DirectX 10 but are very powerful...