[Hampshire] Looking for Linux Set top box

Hi,

I am looking for a STB that I can install Linux onto.
I need:
1) Net boot.
2) Wake on USB (for the remote control. I want the STB to be in a
cupboard, with just the remote control eye outside, so a USB attached
remote sensor.)
3) HDMI output
4) Able to decode MPEG4.
5) Fanless
6) Small, so probably mini-itx.

Essentially, It will be a mythfrontend accessing content from across
the network.
All my TV aerials etc. connect to a central PC, with the STB linking
to them via Ethernet cables.
I tested using a laptop as the STB, and wireless to the central box,
the this kept breaking up the image, so I have to use Ethernet cables.

Content will be recordings I have made from TV, and also my HD Video
camera, jpeg pictures, you-tube etc.

I cannot seem to find one that can do MPEG4/AVC and is fanless.

On another point, I have quite a few IR remote sensors that plug in
using a 3.5mm jack to DVB cards.
Does anyone know how I might be able to interface these to a PC that
does not have the DVB card in it.
Maybe some serial interface or something.

Kind Regards

James