Rev. Voodoo on "Trying To Enable RSS Feed By Category - PLEASE HELP"

http://www.listenupdenver.com/?cat=4&feed=rss2

works for me as a cat feed of your features

You don't have permalinks turned on so adding /feed to the end doesn't work.

If permalinks were turned on

http://www.listenupdenver.com/category/features/feed

would do the same thing

EDIT: more info http://codex.wordpress.org/WordPress_Feeds