I saw this today, which is very interesting. It's basically a short demo of XMBC running on the ARM platform. This is is the start of a really great media centre. I've so far been using Mac Mini's as media centres for their size, however the setup is a little complex and I've no need for local storage really. All the media I watch is on my server.
So the video shows XMBC running on a ARM Cortex-A8 beagle board. The actual hardware is tiny. The operationg system looks to be be booting of a SD Flash Card. I guess it would need some kind of IR control for me to use it and maybe a DVD driver, but these should be doable, both could be attached by USB. I think once OpenGL ES support is working I might see about getting once of these boards. They should be noiseless to.
Most my TV's are old, so I wonder if I can connect it to scart (I'll probally replace the TV at somepoint, but would nice not to be force into it).