Website with Bidding/Offers/Buy Now

Hi , We need a Website designed around the ability to sell advertisement medium & the ability to be able to purchase advertising medium. Basically what is needed is to have a website with all functionality of this: [login to view URL] Our main requirement is to have the ability for advertising providers to login and submit advertising medium for an administrator to be able to approve offers and to have them available for viewing by advertisement buyers to purchase via either via Buy, Bid or Submit Offer. Utilising CMS is must for the front end aswell as we dont mind ustilising 3rd party modules for this whole project.