It all depends on what your budget is.
All from take2:
Amd socket AM2+ Phenomx3 Tri-core 8450 Price: R 1,175
Asus AMD M2A-VM HDMI Motherboard - Socket AM2 Price: R 762
Leadtek nVidia GeForce 9600GT - 512MB - PCI-E Price:R 1,276
Apacer DDR2-800MHz Memory - 2GB Price: R 442
Seagate Barracuda HDD - SATA-300 - 16MB Cache - NCQ - 250GB Price: R 566
iSonic 923 ATX Chassis - 400w PSU Price: R 548
Total: R4769
Monitor: Acer P223WQB 21.6 inch LCD Monitor - Black Price: R 2,503
Obviously if your budget is higher I'd get a better psu
Maybe the Cooler Master Extreme Power PSU - 550w Price: R 683
Case is based on taste so whatever.
Get the HD4850 instead as well:
Connect 3D ATi Radeon HD4850 - 512MB - PCI-E Price: R 2,234
Also a quad core would be in order:
AMD Phenom Quad-Core 9950 CPU - Socket AM2+ Price: R 2,112
Then of course a board with 6sata ports:
XFX AMD 8300 Motherboard - Socket AM2 Price: R 1,161
So quite cheaply.