Any VIA mini-ITX , nano-ITX or pico-ITX board could become perfect media director due to its size, low power consumption and other neat features. The only issue is the UI2 with alpha-blending, which is written with nVidia only cards in mind. But the VIA platform itself is just the best for MD, so this UI2 issue has to be solved some day i think.
For those asking about mounting the thin-client to an LCD monitor - this is very simple as it is standard VESA mounting, which almost all LCD TVs and monitors have nowedays. For such kind of cases (USD 49 without PSU) and many others related to VA ITX platform, please check here:http://www.idotpc.com/thestore/pc/viewPrd.asp?idcategory=8&idproduct=456
Here are some more mini-ITX systems and accessories with quite impressive features and very affordable prices:http://www.mitxpc.com
and check their eBay shop for even better prices:http://stores.ebay.co.uk/MITXPC
Please don't think it is a kind of an AD, I just like those cases and have very good experience with the sellers.