HDMI only supports upto 7.1 channels, so for any thing with more channels you need the optical connection (which the PS3 doesnt have).
That said, Im not happy with the fact that the blu-ray player he sold me doesnt talk about 7.2 in the manual, although it does have an optical and coaxial cable.
***
Now this is my fanboy rant: Interesting enough I can buy a Blu-ray player and and XBOX360 pro bundle (2 games, some offer 3)with games and still have $50-$70 change, where as a year ago it would have been $400AUD more!
Predictions JAN 08
2008 PS3-19.5M(actual 19.5) XBOX360-23M(actual 27.5) Wii - 37M(actual 45.8M)
End of 2009 PS3-27 25M XBOX360-30 35M Wii - 48 63M (revised DEC 08)
Price Point
Mid 2008 Wii $250 Xbox360$249 Xbox360(HDD)$299 PS3 $399
Mid 2009 Wii $189 Xbox360$199 Xbox360(HDD)$249 PS3 $339
Mid 2010 Wii $ 149 Xbox360$159 Xbox360(HDD)$199 PS3 $289
