are you going to use a tower or desktop?There will be 1 or 2 Siemens DVB-C cards and one budget card inside.
i believe not... the cpu alone can reach 70/80 W. but i do not know about idle watts...I would like to keep the idle mode power consumption low. With old K6 based AT PC I have measured idle mode power consumption to be about 50W. Is this nowadays possible at all with recent motherboards, chipsets and CPUs?
i would take some recent cpu and chose a lower frontside bus frequency. so the cpu stays cooler (less cooling) and you save energy. say..use an athlon 2200+ (1.8ghz) and run it with 1,3 ghz...The system will be placed in the kitchen where there are already some noisy devices wo the VDR box does not have to be completely silent. The system will need enough horsepower to play DivX:es, though. It will be a multimedia home server server.