Do you really need a kick-ass machine to decode DVDs and record tv?
No, because the hauppauge card is dedicated hardware for the really difficult part – realtime MPEG2 encoding.
Anything around 2.0ghz or 2000+ is more than adequate for HTPC.
Now if you’re transcoding lots of DVDs to DivX or other MPEG-4 formats, you might want more power. I still think a fast Pentium-M will be plenty good at this, though… and the 2.0 P-M overclocks quite easily, if you’re needing more performance.