I'm selling one that I built 3 months ago, but hardly use.
Intel 2.83 Ghz core 2 quad processor (4 cores).
8gb of RAM
Video card: 9400GT w/ 512mb & HDMI/DVI out.
1 terabyte hard drive.
(~$650 in parts)
Additionally, I've got a 23" monitor, higher than HD pixel counts (2048x1152). (~$200 new).
The desktop could come with Linux or WinXP now, or else Windows 7 next week.
Dells with half as much RAM and hard drive space, and 20" vs the 23" monitor, are going for $800. I put this together for a bit more than that much originally. Offers or questions welcome :)