I run a Pent4 pc as my media centre. Havent yet installed a HD TV Card for PVR usage, still got the good old trusty Straithfield $69 STB (add your own HDD). But I reckon as soon as they get their act together with multi programming that the Fusion HDTV card will find a place

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The HTPC method is great for versatility with new/strange video formats as you can just upgrade yout codecs quickly. If you have a Dreambox 500 you can mount the drive and have a PayTv PVR and so on......My money is with a PC!
Downside though is power consumption if you have it running all the time.