I’m currently managing over 500 RSS feeds (!!!!!), and FeedDemon makes it very easy.
The trick is that I don’t actually read all 500 feeds – there’s only about 50 or so I actually read regularly, another 100 I scan quickly, and the rest are just there for my keyword watches to pick up interesting articles for me.
Works a treat.
When I get a chance, I’ll post some screenshots showing how I typically work with FeedDemon.