I am thinking of selling Digital Products and I'm looking for a nice program that offers me features that include but not limited to:

1. Download Protection(no one ever should be able to download the files except by those who have permission).
2. Bandwidth Control per user-group. (I want to limit bandwidth per user for a daily or monthly bases. Like 500mb per day and 2gb per month). In other words, great management flexibility for bandwidth.
3. Product-Based selling or Member-Based selling. In example, I can sell per product(download per a bundle or file) or Download everything without limits(depending on your user-group).
4. User Management system that can tell me of each user and what they downloaded and how many times they did. The bandwidth they used and all sort of infos.

There are many features that I'm looking for but having these is great. I don't want a script done by an unknown person. I want to buy a secure product by a well known company that give me support.

You will need to have a company to develeop this for you.

The only company that I know of that would have something which is used by 99% of all Adult webmasters and that can do some of the things you speak about is ccbill.com. They don't keep track of the bandwith usage, but they have a password manager together with an good affiliate system.

Have you looked into Share-It to manage your downloads and credit card transactions?

Most scripts will probably handle your needs vice the bandwidth - it might need to be programmed into that process. Payloadz works well with PayPal and might be another way as well.