Hardware Planning

I am planning to build a school lab network that will have to do with architecture designing and using Autocad kind of softwares.
I would like to have Windows 2000 server and 12 Windows Prof workstations for a start.
Is Pentium III or AMD processors should I use, can I use desktop mainboard instead of server mainboard regarding my tight budget and how much memory do I need for the server and do I need managable or unmanagable switch/hub?

Thank you for the help you can give me.