I wanted to mess around with A/UX and the Quadra 650 was the cheapest '040 I could find.  Came with a 320mb hard drive and nothing else, so I eventually pieced together:
 

128mb RAM (+ the 8mb on board)

1mb VRAM

AppleCD 300i Plus (2x tray), rails and bezel

Ethernet transceiver

VGA adapter (don't own a Mac monitor, fortunately this one supports 1152x870)

External 1gb Jaz drive and 3 disks

new PRAM battery