Advise on themes and plugins

Hi, I am new to wordpress, I have had an idea for a site and from what I have read, this may be the best method, but there are so many themes and plugins available, I am not sure which would best suit my needs. So I am looking for some advise.

I require a site with users, so require a register and login ability.
A forum.
The ability for users to review items, each item would have its own page where overall reviews can be seen.
The user would have to select the item that they own when registering, and would only be able to leave reviews and comments for that particular item.
They can amend and adjust the review at any time, and update the comments associated with it.
If they decide to change the product they own in their profile, it would have to be approved by an admin.

Hope this makes sense, and advise would be welcome ??

Thanks,