Should be able to get a 800mhz one for that.
Quicksilver
(previous enclosure)
867MHz PowerPC G4
256K L2 cache
133MHz System Bus
256MB SDRAM
40GB Ultra ATA drive
CD-RW drive
NVIDIA GeForce4 MX
56K internal modem
$1252 at Apple Store Edu.
Should be no problem to get a monitor for $250