That depends on where you put it and how much uptime the machine sees. My cold storage NAS draws 70W idle, but its up time is at most a few hours per week - and I essentially got it for free. Since the 12 disk file server case sits in the basement it doesn't bother anyone with the turbines running.

I thought about going dual Xeon for my desktop, but found that I don't often need that much power (at home) to warrant excessive power draw you mention.