audio over wifi (Linux)

Hey,

Having recently purchased my first hifi setup; I am now interested in being able to stream my mp3/flac collection on my computer and possibly _all_ audio output (i.e. video games). from the computer to my amplifier.

I have seen a friend of mine do this with Apple's Airport Express; however I am using Ubuntu so iTunes isn't really an option (not an ideal one anyway). Is there a similar product that comes with out the of box support for linux? What other avenues might I consider exploring? Ideally I would just like to be able to stream _any_ audio output, without having to invoke special settings for each application.

Cheers,

Andy.

al