Sorry for reviving this old thread, but just picked up a new (used) system on Gumtree for $300.

CPU: Intel Core i5 750
RAM: 4GB 1333mhz DDR3
GPU: nVidia 9800GT 1GB
HDD: 500GB Seagate Internal, 1TB Seagate External

Also came with a 17" LCD Monitor, and a Razer Lycosa Keyboard.

So I think I got myself a pretty good deal and a decent upgrade from what I had before!