Exchange 2000 Std to Exchange 2000 Ent.

This weekend I will be not only be moving mail from the Exchange 2000 Std edition to Exchange 2003 Enterprise, I will also be swapping it to a new domain that I been building. Would I have a problem with the tape back up drive doing this or would it be best to export all mail from the users desktops to .pst files and then importing them back in when the new server is running? I only have 40 users so it it should be simple to export and then import. Any other suggestions would be greatly appreciated. Thanks