Compiling RSS feeds based on search criteria

Looking for a web-based app

[adrock31]

Safari 2.0 has a great RSS function that allows you to search your feeds for keywords, and it creates a dynamic feed for you to read that only displays the posts that result from that search. I think this is really great, but I am a PC user, and don't have this function in my reader.

One problem I have with this though, is that if you are scanning a hundred or more feeds, it quickly becomes a large amount of downloading everytime i want to update my feed list, and a lot of those downloads are not of interest to me.

Is there a service, app, web-based or not that will allow me to enter in several feeds, set search perameters, and then subscribe to a resulting dymanic feed? this way, i read the posts I want without having to download hundreds of posts I never plan on reading but stemming from dozens or hundreds of individual feeds.