plugin for a 3D model shop

Hey guys

Since the beginning of the year I have made a 3d model shop on my website. To sell the models I am using the plugin called “Paid downloads” but as an Administrator I am the only person who can use it.

Now there are some users who want to sell their 3D models too and here is what I am looking for. A similar plugin like “paid downloads” but :

– to send an email to users when they have sold an item
– to let the users check their models and how many times their models were sold.
– to be able (me) to adjust a tax, like 10%-15% of the price.

Is there any plugin like this ? and if there isn’t does anyone know how much it will cost to make one ?

Thanks 🙂