CMS with RSS aggregation, user submissions, social network integration

I'm looking for a CMS which would aggregate news from multiple blogs.

[chaosas]

Hello,
I need advice for the best CMS for my needs. It could be a specialized content management system for RSS aggregation, or something universal like Joomla, provided it has the right modules.

What I want to do is aggregate news posts (title + excerpt) from multiple blogs. I want my visitors to be able to submit their own blogs for the site, where I'd be able to approve or deny them. Obviously I'm looking for something automated so I wouldn't have to manually add every feed, but rather simply approve it and it would be added into the news.

Also the site should list a dynamic list of blogs that the news are being aggregated from, and of course the news themselves sorted by date.

I have thought of using something simple like Yahoo! Pipes with a simple PHP-based RSS parser, but that would mean a lot of manual work.

Do you know any CMS that would be suited for my needs with minimal customization (since I'm not a programmer)?