I'd build a great system around the following:

Antec P180 ATX Advanced Mid Tower Aluminum Case 4X5.25 1X3.5 6X3.5INT No PS W/ USB & Audio Ports
$163.31

AMD ATHLON 64 X2 4400+ DUAL CORE PROCESSOR S939 TOLEDO 2.2GHZ 1MBX2 90NM RETAIL BOX
$663.31

OCZ Rally High Performance 2GB USB2.0 Dual Channel Flash Memory Drive
$153.98

Total = $980.60!!!!