Case: Antec Three Hundred (great brand and a great case for the money, pretty cheap as well)
CPU: Intel Core 2 Duo E8400 or Q6600 (Q6600 is fine but the C2D should perform better because it uses 45nm technology, not 65nm)
Mobo: ASUS P5Q or P5Q Pro (good brand, should work fine)
RAM: Corsair 4GB DDR2 XMS2 PC2-6400 (DDR2 800 is probably the best bang for buck speed you can get for mem right now, DDR3 isn't worth it right now unless you're on an i7)
GPU: ATI Radeon HD 4830 512MB or 4850 (the 4830 is a great GPU, currently on par with 9800GTX so great bang for buck card, if you can afford it, get a 4850)
HDD: Any good 250 or 500 GB HD should do, make sure it's got a good cache size such as 16, 32 MB and a SATA interface, good brands are Seagate and Western Digital)
DVD-RW: Asus DRW-22B1LT 22x (should work great, or there is the alternative of a Samsung SH-S223Q/RSMN 22x)
Cooling: Buy 1 or 2 case fans and a good CPU cooler, Arctic Cooling Freezer 7 Pro is good for LGA775 CPU's)
PSU: OCZ StealthXStream 600w
I don't know how much all that would be in AUD, around £600 or £700 here though + VAT. If you want to keep the setup you posted above azn, I'd take out the PSU and replace it for a good 600w, a better CPU e.g. E7300 or E8200, better RAM and at least a 4830.