CD Baby - Reverbnation - Selling Music

I currently have a Joomla website with Jomsocial User profiles and music collection for users to upload music. I need to integrate the ability for my users who upload their music to sell their music on my website. I already have install software and plugins from [login to view URL] the user will need to be able to connect their music upload account to their paypal or money bookers account. Their is currently a shopping cart feature built into the music software. However it isn't very user friendly and the software allows you to dowload the song without paying first. I need assistance improving the function for uploading and selling music on my website. Similar websites are CD Baby and reverbnation. If, you have done similar projects please post the links or your portfolio.