If you haven't found the software package you look for, then I think you must try Latitude. It's a great tool to better manage your projects, tasks and documents. Tasks can have sub-tasks and you can assign them to a specific user. You can notify users about their tasks via email, manage documents such as drawings, spreadsheets and emails, it has a billing system to quote and invoice job costs, and user timesheets can be exported to accounting software for payrolls. You can check more of its features in this website: http://forums.xisto.com/no_longer_exists/
