We are looking to develop an intranet that will have department pages (HR, Sales, etc.), each department's landing page is going to have its own news/announcements section and downloads (PDFs and Docs). The site will also have a calendar of events and a directory of employees that needs to be searchable separately. What are the essential plugins for such an implementation to make posting of content to different sections painless? Should a CMS solution like CustomPress be used? I would appreciate your insights.