I built my own system.
SPECS:
Motherboard: Gygabyte (not sure of the number) with 4 DDR slots, 1 AGP, 4 PCI
CPU: AMD Athlon 64 3700+ ~ 2.2 GHz
Memory: 1 GB RAM using one of four slots on motherboard
Hard drive: 200 GB
CD-ROMs: 1 CD/DVD R-RW
Floppies: None (dumb thing stopped working)
Internet connection: Linksys Wireless (go me!)
Sound system: Creative Live! 24-bit 7.1 Surround Sound
Box: $100 box with transparent side, blue lighting and gauges which show my Volume Units, CPU temperature, and Power Supply Fan Speed
Monitor: 17" LCD from Norcent
Mouse: Cheap trackball-less mouse on a USB cord
Keyboard: $50 Zboard with keys that come out with the flick of a switch, and can be replaced with a gaming keyset and back; this makes it easy to clean the keyboard, too!
The total price for this machine came out to about $1200. But it was well worth it.
[edit]I now have two mice plugged in at once.[/edit]