I'm fairly new to web design, but I have prior IT experience and have done some light coding. I have an idea for a website, but despite researching for the last 8 hours I'm still confused as to what platform(s) and tool(s) I should start learning / using to build this type of site. Here is the main concept:

- End-user content creation & rating of other user's content.
- After registering & logging in, users can upload or link to video or audio clips to be rated & evaluated by other users (both numerical rating and typed comments, a la Amazon).
- Each new content added by users would dynamically spawn a new sub-page to site (not published by site admin). Users will also have their own little profile pages with their submissions and review comments / ratings of other user's submissions.
- Ideally embed videos from Youtube or other video hosting websites so my site doesn't incur the hosting costs. Would be nice if users could upload videos from my site and have it actually uploaded to Youtube in the background to simplify the whole thing for users, but not an absolute requirement.
- Aggregate ratings & view data so main home page can list top rated videos, most viewed, etc and also have sponsored videos.

The key to the whole idea is wrapping each user-submitted linked media (e.g. video) with metadata (ratings & comments) to create competitiveness, maybe for contests, but at least to promote popularity ratings.

Is there a CMS platform out there that can simplify the creation of this type of site? Seems like most CMS platforms are oriented towards a site admin pushing out content instead of users creating it for themselves. If so, what would you recommend? Joomla? Drupal?

The site will also need to be robust enough to handle lots of traffic in case it takes off. If a CMS won't work, what tools should I be looking at? Obviously a database will be involved, but I'd like to know if there are at least templates out there for use or purchase to get a jump start. Thanks in advance for your input!