Hmm …
I really am a fan of Alfresco and am a strong believer in its functions, its future and that a good community can support and boost this all. You can do it all, I would say, with slight modifications. But "share" as application is not very far yet and still in developement. It would be great if your company could further this by adapting share to your needs and giving back these features to the community.
But only, if your primary function is document handling. For wiki handling, I would suggest Atlassian, for community interaction in a social network, I find Jive quite impressive. We are using both at my company. Drupal is good as well and liferay is trying to get there, but the Wiki is not usable for non-it people yet.
So coming back - check out a combination of Alfresco and Drupal, maybe ?
Norgan