Best option for “subscribe to comments” feature

Hello, I have a small WordPress install, that is a help site for computers. We get a lot of comments.

My current workflow is to take the comment notification email, follow the link, and reply to the comment. I then reply to that initial email, pasting in some template text, and a url to the comment reply I created.

Before this workflow, users rarely remembered to come back and look for responses to their comment. I took it on myself to hand manage this with emails directly to the commenter. My users are not up to speed on RSS and/or bookmarks for that to be an option; plus, it is too much work and less than ideal.

In searching, I find there is a large offering of comment notification system plugins for WordPress. I do not know which one to use. I am looking for notification of a reply to the original commenters post. This ideally would only notify them of a reply to *their* post, but it would be acceptable to just notify them of any comment. Or give them an option, along with subscription management that is not too confusing, and does not require an account. I can not require accounts, *that* is not a possibility.

I see the notification of *any and all* comment as problematic, as comment volume is high, and I will often wait a day or so to reply, meaning I am slamming out 5+ comment replies per post, and would not want to hit a user with 5+ emails, in addition to the emails notifications they got from other comment replies and new comments.

What are my options? What are the pro’s and con’s? Is there sort of a de-facto standard in this type of plugin that most custom WordPress installs are gravitating towards?

Thanks for any suggestions, I currently am at a loss as to where to go, and would like to avoid the search, install, test, dislike, uninstall, rinse, repeat process.