membership program and original wordpress users

So I need a membership program that:

Will allow for only a section of the site to be available to signed in members. The rest of the site can be view by the public.

I would need it to be incorporated with the existing WP user database so that these users can receive newsletters from a different plugin - that accesses the same database.

The members would have access to their own accounts-

None of the member levels are paid.

I looked at your member program but was confused as to which way to go, and if the member database was separate from the WP user base.

Any ideas for me?