HTPC - 460, 5450 or 6750

Hi,

I have just built a HTPC to power a 50 inch plasma and i am having a few issues. The PC is plugged in to an Onkyo Amp (608) which supports TrueHD and DTS-HD Master, the graphics card MUST:

Allow bitstreaming via the HDMI to my amp for HD sound
support playback of 3D Bluray via both original disk and ISO from a virtual drive.
playback stutter free
preferably take on some of the load from the GPU as it maxes out at the moment.

I currently have the 5450 and i get some stuttering on playback occasionally, certain players struggle to play back with HD sound, PDVD and TMT5.

I wont be playing games on this PC so that is unimportant.

Any suggestions?

I have an Onkyo AVR (876) & 5450 also, and it all works like a charm feeding my 50" plasma & my projector.

What drivers are you using for audio over HDMI? You need to use ATI to get bitstreaming working properly in TMT3 (TMT5 is maybe the same?). I can bitstream without issue in TMT3 and Media Player Classic (via Ffdshow).

As for stuttering, do you match your refresh rate to the source material? My HTPC runs @ 23.976hz 99% of the time, and I switch to 50hz or 60hz based on content.