Most of the items on your list have to do with functionality and not the look of the site.
WordPress uses themes and plugins. Plugins can be added to alter the functionality. Themes are primarily for changing the look and feel, although a lot of premium themes try to wrap as many features as possible into their themes.
I would recommend browsing the theme repository for something you like. Then, just use plugins to provide the functionality you need. If you really want everything as a complete package, you will want to look into premium WordPress themes. Just be sure that you buy from a company or individual who will support their product.
Here are some plugins that will do what you want:
- Community option - BuddyPress (Note: if you use this plugin, you will need to make your theme compatible, unless you use a compatible theme from the start.)
- SEO Friendly - Headspace 2 SEO (If you use BuddyPress, you may want to check out BuddyPress SEO too)
- Music and video player - There are a lot of options out there, just browse the plugins repository.
If you find a great theme (that has been recently updated), use plugins for the functionality and all you want to change are the colors, CSS makes it really easy.
All that to say, just find a theme that you like the look and feel of. Know that the functionality and colors can be changed, usually, quite easily. Just be sure that the theme you chose is frequently updated so you don't have to fix it yourself when WordPress starts "outgrowing" the theme.