These are the system components that I plan on buying for the other 4 boxes.
As you can see, I haven't decided on the case and power supplies yet.
Comments welcomed.

$99.99 CPU
Intel Pentium E2140 1.6GHz Dual Core 1MB 800MHz LGA775

$65.99 Motherboard
Foxconn P4M9007MB-8RS2H S775 1PCI-Ex16/2xPCI/2DDR2, w/VGA/SOUND/SATA/LAN/MATX
Memory: DDR2 667 / 533 /400 x 2 DIMMs, Max 4GB

$59.17 Memory
Kingston KVR667D2N5K2/1G 1GB Kit 2x512MB DDR2 667MHz

$79.99 Graphics Card
Asus EN7300GT/256 256MB DDR2 Silent PCI-E w/HDTV & DVI Retail

$83.99 Hard Drive
WD WD3200AAKS 320GB 16MB SATAII Western Digital

???? Case and Power Supply