kinda off topic anyway, i have experienced beryl on intel 855gm, 950 and gma3000 series.
beryl runs acceptably fast. as for hd, i can play 720p video on my laptop with gma3000 fine without beryl. never try 1080p though.
im not into the idea of media center pc. i prefer the new xbox360 hdmi + hd dvd drive
hdtv on linux? hdcp? bluray? good luck to you