I have a 5750, PowerDVD 9.0 Ultra fully patched, and an Onkyo HD receiver. Bad news, there is currently no option to bit-stream Hi-def audio to external device, we are still waiting for a "patch" from cyberlink, see this forum post on Cyberlink's website:
http://forum.cyberlink.com/forum/posts/list/8425.page
This "patch" from cyberlink was supposed to be out a month ago. Also, with the latest patch, as noted in the link above, cyberlink has effectively broken regular DTS and DD 5.1 bitstreaming. Any luck with any of you guys on this?