HTPC to play H264 with hardware acceleration

[velis]

So I have an old S939 Athlon sitting around and I want to use it for my HTPC + file server.
Specs:
Athlon X2 @2GHz
2GB RAM
GeForce 6600GT
NForce4 SLI MB

I was thinking of upgrading the graphics card to ATI HD4350 256MB - not much gaming will be done on this comp
Also, a BD player will be added and 3 additional disks (WD Green edition) to host the media.

This setup will have a seriously hard time to play back full HD H264 content on the CPU.

So my question is: can the 6600GT help decode H264 video?
If not, can HD4350?
If not, what can?

I need as much acceleration as possible, no need for CPU to work out if there's enough HW out there that actually does it. I'd like to keep this setup as cool as possible.

[velis]

I've researched problem further and this is what I found:
mplayer (and most MCE front-ends) has VDPAU support, but only for newer nvidia graphics cards. 6600GT is left out, unfortunately.

I was testing this in Ubuntu 8.1 and 9.04 and sure enough no player was able to keep up with 1080p.
I have compiled the mplayer-mt branch though and it manages to play 1080p with minimal frame dropping (unnoticeable). There are only a few situations where the CPU can't handle the stream.

It seems though there won't be a viable setup for me under Linux for a while since the mt branch is only one player. Most of MCE front-ends don't support this branch.
Maybe I should go back to testing this under windows... Seems DirectShow has much better support for what I want.

[dott]

I believe(not sure) you can use coreavc decoder under linux, a little search give me some google-code hosted patch for mplayer, if this works the difference will be significant.

Under windows there are more alternatives, coreavc and divx7 decoder are both better than ffmpeg/libavcodec(mplayer,vlc,xine,ffdshow).

If you use a 8xxx/9xxx nvidia card and coreavc with cuda enable, the cpu will become less important.