Yip ram is really cheap right now, but a 8GB kit will still set you back around R550.
Something a long these lines:
i5 2400 (Quad Core with Turbo)
ECS P67H2-A3 (Decent board)
Patriot G2 DDRIII 1600 2x4GB
That'll set you back around R3250
Alternatively you can go for:
AMD FX-6100, 3.3GHz (6 Core)
MSI 970A-G46 AM3+
Patriot G2 DDRIII 1600 2x4GB
That'll set you back around R3100