@gnoboot
I saw your recent blog posting about cpu power management. Great that you have this still in mind.
As I read in serveral forums linux powersaving with modern (haswell) cpu is quite tricky, but I'm not a linux developer . Also sata link power management seems to be a big thing for good idle power values.
http://www.heise.de/forum/c-t/Bauvorschlaege-fuer-PCs-und-Server/Re-Bauvorschlag-c-t-19-13-Experimente-mit-Ubuntu-13-04-x86-64/posting-401185/show/
Best power management is only achieved in Windows* and when several drivers are installed (Intel Inf, RST, GPU, Audio, Lan, MEI).
*http://www.heise.de/ct/artikel/c-t-Labs-5-Watt-fuer-eine-Selbstverstaendlichkeit-1948002.html