Valve have been showing off their Steam Machine prototype to tech bloggers over the weekend, including Wired, The Verge and Engadget (who have split their version into three individual articles). This is the first time we get to see the actual physical hardware, which looks a lot like a Small Form Factor build you may do yourself.
The only major difference is the case itself, which is designed specifically to fit powerful hardware into a small space. Using 3D printed plastic shrouds, individual cooling zones are designed to keep the components from heating each other up.
Unless things change, this model is the only Steambox hardware that Valve will ever release themselves. During CES in January, they will announce the actual third party hardware that people will be able to buy in “mid year” 2014, and more details on the system.