Parsing feeds...slow

I need to parse about 50 RSS feeds and display the latest posts from each sorted by post date. Right now I have a cron job calling a rake task saving the feeds locally every 5 minutes then I’m using simple-rss to do the parsing. Even though the posts are local its still very slow to parse and display all of them. Anyone have any other recommend approaches (caching, etc) that might improve this? I’d say an ideal refresh time would be about 5 minutes