They aren't Steam Machines, but they are made for the living room. Origin PC has put up a teaser for their Omega line of computers that look like they fit well in the living room space.
Not much is known in terms of specs and pricing but expect options such as SLI, water cooling, and multiple OS capabilities. From the looks of it, there's one long box option, which looks to be good with multiple video cards and a water block along with a more traditional media center case, which would fit a nice single video card option.
You can sign up to be notified about the availability of the line, but expect them to be out sometime in 2015.