Free Mambo

I am trying to restart a media site we had years ago which focused on original as well as some user-generated content; specifically images and videos with the ability for users to rate and post comments, etc. I know of several CMS’s like phpnuke/mambo/joombla etc however these don’t seem quite right.

I assume the websites I described payed a programmer for a custom CMS, however I am hoping there is a similar open-source (or cheap) alternative for media-based websites/online communities.

We already have the domain, hosting, and a very knowledgeable staff.

What would be the best way to go from here?

Thank you to anyone who can provide assistance!