My home server is a pig and draws about 100 watts idle.

You should try running powertop on it. It will scrape sysfs and look for things that seem misconfigured, and suggest changes to fix them. On one of my machines it enabled some peripheral power saving mode that made a pretty dramatic saving!

(I also heard that it sometimes suggests power saving modes that are usually switched off for a good reason, like apparently you really don't want some USB controllers going into certain sleep modes as they take seconds to come back).