I've been tasked with coming up with a solution for an internal knowledge bank to house information for our company on best practices, techniques, tools and processes.

I also want a system that can allow users to post links to industry news and facilitate discussion around each news item.

My first thought was to use Wordpress, or similar blog software.
My second thought was to use blog sotftware for the news/discussion site, and a wiki engine to power the knowledge bank.
My third thought was to use a single system - possibly a wiki engine - to power everything.

We're most comfortable with PHP and an Apache web server, but wouldn't rule anything out at this stage.

Some desired functionality:

RSS feeds to alert to new content (Knowledge Bank) and new stories (Industry News).
Ability to attach documents (.pdf, .doc's) to pages.

Any insight much appreciated.