Hi,
I have been developing ecommerce websites since the year 2000.
You said that you need it better than the referred website, but what I can see is that anything could be better as I see it as a bad one. I am awarded this project, for sure I will create a much better one with the features you like, when someone pays for a product they will be able to download immediately, you can make a group of products as one bundle with discount and one payment to download the bundle product.
With a payment gateway and many other features.
Please award to me, I am ready to start working right now.
Regards,