the MK802 will run Ubuntu - and it is about that wattage - though my RPi is more stable than the MK802 over long periods
My MK802 II that has been running for weeks on end with no issues wants to disagree with you, but he can be a little feisty, so I'm posting on his behalf. Some versions of Ubuntu are more stable than others, but I've found one that's rock solid on my device.
https://bitcointalk.org/index.php?topic=7216.msg1376515#msg1376515I just checked, and it's been running my Single for over 2 weeks with no crashes, hiccups, or anything. And this is over wifi, powering the device off the powered USB hub that it's then controlling.