The team of the open source mediacenter software XBMC has published a video showing how XBMC runs on an ARM system. The small, energy efficient BeagleBoard runs on a 600 MHz processor and supports OpenGL. The hardware is also compatible ewith HD video output through DVI and WiFi by means of a USB dongle.
By running XBMC on such an ARM system, only limited space is required, and energy consumption significantly drops as well. The hardware needed for these ARMs is also relatively cheap. The mediacenter software does not run flawlessly on the architecture yet, leaving room for improvement with the developers.