If anyone knows of an alternative that's in the $100 (US) price range, runs linux, and will make my life easier, I'm grateful for suggestions.
Oh, and it needs to play nicely with a USB-to-ZWave dongle and one of the major open-source home-automation packages that can do lighting controls.
EDIT: I forgot to mention that I want it to reside in a closet that has very little ventilation. So I'd be leery of deploying a cheap used x86 system, even if the price way right.
EDIT2: Holy crap I'm being high-maintenance here. I should just do a damn Google search like everyone else.