Registration form

I currently have over 1100 “subscribers” to my blog, but I’m not sure who they actually are or the specific interest that they have in my blog. I have two plugins in the operation of my blog that apparently allow users to “subscribe” to various posts. These are “Subscribe to Comments” and
“Subscribe to Comments Now”. But most of these “subscribers” do not leave any comments, and some of them do not have valid email addresses. I would like to install a form in a Page on my blog that would invite users to “Register here” to be able to comment on my posts, subscribe to RSS feeds, and get a newsletter about my blog when I decide to publish one. How can I create such a Page and what plugin should I use to enable interested users to do this? I use the Aspen Theme, and my browser is Firefox and my OS is Windows 7. Here is a link to my blog: https://www.christianityetc.org/blog. RAny help with this matter would be appreciated.