I asked a somewhat similar question last Christmas--you might find some general guidance on buying on the cheap in that thread. And I'll reiterate something I've seen many places--you wouldn't believe what large companies throw away. I'm still kicking myself for not picking up those beautiful old IBM servers--3274's I believe--out of the dumpster last summer before the guys I worked with beat me to them.
in reply to Ultimate Server, Minimal Currency
They laughed at Joan of Arc, but she went right ahead and built it. --Gracie Allen