Personally I'd recommend VLC - (click on link) _ (choose nearest mirror site) as it has in-built codecs & is generally very reliable. It can also play most audio formats. It's good for both audio & video streaming & you can also downld extra skins. See what it can do here http://www.videolan.org/vlc/features.html

For extra codecs, see CODECs list and alternate players for Movies as you'll find links to codec identifiers, etc.