Killawatt is as cheap as it gets, pretty much.
Gpu load and idle power draw for "Cinema-Plex" in sig.
Sub-Tropic Thunder in my sig draws around 450watts at "idle"; including three monitors and speakers.
Idle=couple dozen tabs in IE, email app, steam, Skype etc running in the background
I would not recommend running through the Killawatt 24/7 if you draw more than 500watts regularly as the socket its quite hot; hot enough to scorch the plastic.