How fast for HD Video?

[Hamzter]

I'm looking for a media centre PC to use in my houses living room, we've got a 720p HDTV in there so we'd like to be able to play HD video if at all possible. What kinda speed processor would we need to be able to play HD (I know there can be a lot of variation but we only need a rough estimate)? We're planning on getting a box off ebay, our price range is pretty low though. Max we can get is about a 3GHz P4 system, I doubt this is enough though?

EDIT: Also, what affect does the graphics card have on playing video? As far as I know the graphics card has little to do with it, not sure though, most of the systems I'm looking at have integrated graphics and no AGP!

 

[Cold_And_Miserable]

With the right software a DXVA capable display adapter will allow 1080p VC-1 to be decoded effectively even on older systems. ATi cards are generally superior at video decoding and produce a better image quality than Nvidia solutions.
X1900 series, 8800GTx series, 2600-2900xt series should suffice
Without the above only the latest Intel CPUs would be able to decode it consistently.

 

[BENdage]

I have a media server set up that streams HD content to my xbox using TVersity. Its only an old Athlon 1700 DLT3C JIUHB overclocked to 2.5Ghz with a 64mb geforce2 ti and it streams perfectly, so I'd have thought you'd be ok with that P4.