This is all very cool, but I can't help but think that it would be easier to get a used 12" HP 2530p for ~$150, install 2 hard drives inside it, install whateve

This is all very cool, but I can't help but think that it would be easier to get a used 12" HP 2530p for ~$150, install 2 hard drives inside it, install whatever distribution of Linux you want and connect it via its fast Gigabit port. Less headache (though not as fun!), more storage space, less latency, more processing power at a still very low power consumption :-)