Go to
http://www.microsoft.com/windows/windowsmedia/thirdgen/default.asp and be amazed it apears that WMAv9 ( corona )will suport 6 channels of audio and WMVv9 it's the best thing before stone age here are some examples:
"Building on the industry-leading Windows Media Audio and Video codecs, Windows Media "Corona," which was previewed in December 2001, introduces two new professional-level audio and video codecs. The new Windows Media Audio Professional is the first codec to enable Web-based delivery of 6-channel surround sound with full-spectrum, full-resolution audio (24 bit/96 kHz sampling). A new version of the Windows Media Video codec provides a 20 percent efficiency boost compared with the previous version and introduces the ability to provide high-definition 720p video resolutions at file sizes half that of today's DVDs, for local playback on the PC."
The actual version of WMV take more or less 15 seconds to buffer with the new version it only takes about 2 seconds, take a look.