Sage is a lightweight RSS and Atom feed reader extension for Mozilla Firefox.
It’s got a lot of what you need and not much of what you don’t.
Sage - RSS and Atom feed reader extension for Firefox (...)

Tell BlogRovR the blogs you like, and from then on, as you browse the web, Rovr instantly fetches you posts from them which link to whatever web page you’re viewing.

Rovr’s tray slides in to show you summaries of the posts about the current page. Click on a summary to read the full post, right on the page it’s about.
BlogRovR (...)