Thought i would bring this up I downloaded this little piece of softwere from fhg's website and it's awsome brings you 5.1 suround sound to you in youre headphones If you have winamp i sugest using the plugin then using fhg's standalone player. i'll post some links and let you decide.
Fraunhofer IIS MP3 Surround

I tested MP3 SX Converter, which is used for for "upgrading" MP3 stereo files into MP3 Surround files. I ran Daft Punk-Da Funk (192kbps) through it and it turned into a 224kbps and slower than encoding to Flac -8. Not worth it. I'll stick with good ol' stereo, 5.1 is just placebo

Looks interesting, I'll have to check that out. (becides, I figure I'll get it for free while I can)