which module to use for feed filtering?

Hi guys,

I am a bit lost and need your advise. I want to be able to simply filter all feeds by my keywords.

In other words, if I subscribe to many many news feeds (let say all available RSS feeds from a many many websites), I do not really wanna read all that stuff. Instead I would just like to set up my own keywords and filter or delete the rest of the feeds downloaded from all these websites.

I am using drupal 6. I have check already built-in module "aggregator" and "aggregation" module - it is not possible, right?

Thank you for advise.