This is a picture of my setup. On the left you see the XBMC frontend mobo, an Intel DH61AG. It will probably run a windows-based XBMC.
On the right, partly covered by the dual tuner board, is the Intel DN2800MT dual-Atom board, which will run the TVHeadend server. A nice feature is the SSD with both read and write speeds in exess of 500MB/s. Unfortunately the mobo doesn't keep up :(
Both boards have built-in PSUs, so all they need is an external 19VDC input.
The case is a silverstone ML02MX with a built-in iMon LCD and remote control.
PS. You'll have to edit the downloaded filename before You're able to open it. For some reason there are apostrophes pre- and appended to the filename...