How many active afp/smb users on intel xserve?

Hi Does anyone have an estimate on how many active (simultanious) afp/smb users the intel xserves (standard configuration with 2 GB of ram) can handle? It would be a setup at an advertising company where they mostly work on midsize files (around 3-4 mb) on the server. The server is not going to run anything else. Thanks, Peter