Need suggestions for Beowulf cluster enclosure

I have a few (3) computers linked together in a small but growing Beowulf cluster. I plan to add nodes to reduce the time needed to solve jobs. As I add more compute nodes, my floorspace decreases. Is there an inexpensive solution that will allow me to add more nodes to a common enclosure?

Each node will use a SATA hard drive. I will need a DVD drive for the Head node. I'd like to connect a keyboard/mouse/monitor to the Head node but it's not mission critical since I can connect remotely.

It would be really nice if I could find a rack of sorts that houses a power supply, motherboard and drive on each "shelf" that I can add as I expand the number of nodes. All the server racks i've found either dont use SATA drives or use some other connection to access hard drives.

Thanks!