Content Managed Website Build

I have an existing website and I need it updating.
Must allow new users to register on the site and upload potentially large files which they can then sell via the site.
Must include a control panel login area for users to manage their uploads, add descriptions, upload images, set pricing, view sales, delete etc.
Must also include registration for customers to login and download what they have purchased.
So integral cart / payment system will be needed.
Also needs to integrate with http://soundcloud.com to allow audio streaming.
Also needs subscription system for users over 4 tiers.
Also needs a master admin area for me to oversee various areas of the site and make changes.

The site is fully designed (the graphical elements, layout, function, user areas etc) - but I need somebody to handle the programming / database side of things.

I can submit much more detail to interested parties.
Thanks