Hardware and performance

Hello everyone! I am looking for expert advice on the following scenario:

A Moodle server being run on a LAN only (not Internet hosted) for use by about 500 students maximum (as a worst case scenario).

I wanted to know what you would recommend as far as processor, amount of memory, and disk subsystem.

I hope I can get away with using serial ATA for the disk subsystem since SCSI is so expensive.

Thanks for the listen and comments are appreciated!