My word, we're getting into complicated realms here. Sorry pjh that you couldn't connect directly from those links.
Okay, what did I do that made things work?
1. FFox 2.0.0.17 > Prefs > Feeds > Subscribe to the Feeds using > Choose Application > Quicktime Player
2. SysPrefs > Flip4Mac (too many settings to list here, but fiddle about - check back if you want, I can post screenshots)
3. As VT says, R-click on the transfer rate rather than the station name (I R-click only to get the station in a new tab - I prefer to toggle (Cmd-~) between tabs rather than use the back arrow).
PS. I wonder if the 'stuttering effect' may in fact be the playback exceeding the streaming rate. With one or two stations I click Pause to allow the feed to progress to a minute or two ahead of the playback. Incidentally, doing that allows you, the user, to skip or slide past any "Bad" music (to quote Dr X), or get past crappy, intrusive ads or banal and trite news items.