There have been many threads on this very topic.
Check here: http://www.cadtutor.net/forum/showth...hitecture-2011
or here: http://www.cadtutor.net/forum/showth...D-Architecture
Also check on Autodesk's website for minimum requirements for the software you plan to run. If you cut corners and try to do this on the cheap, you will not be happy with what you get.