This is a prototype Steam Machines box from iBuyPower, courtesy of our friends at Engadget. The box comes in two flavors (codenamed "Gordon" and "Freeman," of course), as the center strip is either clear or black when not illuminated with varying colors.
While iBuyPower wasn't willing to share the specs of its version of the Steam-powered hardware, it said the system will run Steam games at 60 frames per second in 1080p. The system is expected to be ready for a 2014 launch, and the two prototype models currently run an early build of SteamOS, the operating system Valve announced would be on its own Steam Machines hardware. Both were announced alongside a Steam Controller in September.
Much update: The Verge reports that the system will include a "multicore AMD CPU and a discrete AMD Radeon R9 270 graphics card" and comes with a 500 GB hard drive, bluetooth and Wi-Fi capabilities. That CPU is very core.