So it looks like the svn version of mediatomb (which will become 0.12.0) now supports streaming PCM audio to the PlayStation(R) 3! This is super good news. So I went and updated my Python shim between Sipie and Mediatomb to output PCM.
You can get mediatomb-sirius.py from my CVS repository by visiting this url:
http://bagend.ub3rgeek.net/cgi-bin/cvsweb.cgi/misc-scripts/mediatomb-sirius.py
Once I have the config sorted out, I will post more.
Edit:
I got FLAC streaming working, and shot a quick video of it in action.
Showing off Mediatomb transcoding FLAC to the PlayStation 3 from Matthew Ernisse on Vimeo.
Edit 2:
I got the sirius stuff working finally, had to overcome a few really annoying behaviours of all the bits involved, but it seems like it is working pretty well. You can head on over to the http://www.ub3rgeek.net/wp/sirius-on-the-playstation-3/ page for more details and another video.