CSB does many things, and interfaces with many others. Also allows programing languages to be used in and with CSB pages (psp, java, javascript, cgi, etc).
Password protected pages can be done in CSB in several ways.
Individual subdirectories for each person can be done with CSB too.
Registering Email sends confirmation to two addresses is simply a script that is implemented, some can be put into CSB.
BUT then you get into another issue: editing contact info, daily and past purchasing history.
By putting this into the mix, I would recommend you look at shopping cart software (maybe ZEN) that allows individual registration, contact pages that can be modified by the individual, that allows orders online (with or without payment online) so they can be tracked. Tied to SQL database, it would be light and easy to use for your customer. All of it in ONE unit. No CSB. You could have a main page with CSB that points to the login, etc then put the shopping software into its own subdirectory.
Take a look at this thread. Check out the site to test out software BEFORE you install on your site.
Many hosts have Fantastico and other software installation packages that make intalling these things fairly easy.