160W lower idle. Replace heavily overvolted OCed PhenomII with undervolted AthlonII or Sempron and you're mostly there.
^This. Also, I have no idea what power supply the OP is using. If is PSU is heavily loaded, efficiency will drop. I was using a Seasonic X-1250 which is built incredibly well. It's rated for 104A on the 12V rail alone. Me only loading it 50-60 percent makes things that much better. ...not to mention that the PSU is just efficient in the first place.