Application design

[eluser]VirtualDevel[/eluser]
First off, thanks for the time out to take a look at this. I'm working on a project that will have some basic objects, users, groups, etc. My thoughts are to create class or libraries for each of these. I have begun with a User class for basic user related tasks, login, logout, check if exists, update and such. I have an admin controller which loads the user class and through this handles such requests. I am about to begin one for the groups. Now, this is where I'm a bit confused, is this an incorrect way of going about such things? Should I instead create a new controller for each item? I feel as if I am in a way breaking the use of the framework as I am writing seperate classes and using one controller for most of the tasks. Thanks.