want rss feeds to display different # of posts for each cat

my blog is set to display ten posts But i have some category posts that i want to display different numbers of posts. im looking for an easy yet proven edit to control # of item/post from specific categories. these rss feeds will be displayed on my website. if no edits are available would settle for a plug in, all help is welcome

my blog > http://psychic3000.com/wordpress/
my website > http://www.psychic3000.com/index.html