Which plugin to use?

I'm trying to figure out which plugin we need. We have about 5 different email updates that we send out and need a way to manage the users and send the emails. It would be great if the newsletters were archived but it is not necessary. They can also be straight text and not html.

Allow users to sign up for the email newsletters they are interested in.
Allow users to unsubscribe for the email newsletters.
A place in wordpress to write the newsletter and send it, preferrably without paying a monthly email sending subscription cost to some external service.
The plugin needs to be managed in the sub-sites. The Mass Email plugin seemed like it could only send to all users across all our multi-sites via the Network Admin location.

I'm wondering if its e-newsletter but am wanting advice!

Maybe even the base question is: should i be using multi-site for this at all? It's a website for a friend and so am wanting to use it under my multisite so i can do all the updates from one place but we need to have separate users registered. Your manual said "Site -> Network (a group of blogs are tied together, usually supported by the main blog where registrations are accepted" so I'm a bit confused. Can sub-sites have their own users registered?

We have Multisite 3.2.1
Thanks so much!