You coud go entirely fan-free with a mobo such as the VIA EPIA EX10000EG:
http://www.via.com.tw/en/products/ma...erboard_id=450
This has a DVI output which you should be able to connect to HDMI with an appropriate lead.
You could cut out any hard disk noise by using a CF card instead, and fit it all in a fairly small case too. But watch out for the PSU though.
I've built a SFF PC for Mrs A using an EPIA M6000 in a Venus case. However, once it gets going, the PSU fan is quite loud.