I've been repurposing enterprise grade servers for years, first one was a based on an i386, various Pentium 3/4, most recently Dell R710 with dual Xeon, redundant psu, loads of RAM etc.
The Dell R710 idles about 70W with 5 x HDD, 10GBe and a PERC card. It goes up a lot more when I get it to do...