PHP or something like Disqus for visitor comments code?

I’ve designed a site in Dreamweaver (haven’t launched yet) & need to add visitor comments to many site pages. Someone mentioned PHP script for visitor comments, or download Disqus. Any thoughts? I want it to basically look like Yahoo news articles’ visitor comments section - ie, clean, simple, avatar, replies. Thanks.

Here’s an alternative to Disqus:

My preference would be to use a CMS for the site, though, as it makes management of the whole site and things like comments a lot easier.