Yeah a PVR card is a good start as there's very little cpu overhead as the encoding is all in hardware. I started with a 250, some people use the 350 for TV out but think it's all too much hassle, you might as well get an Nvidia card install the driver, add two lines to your xconfig and get really good TV out. I've now got two DVB-T cards which are much better.
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Cheers,

Andy M