The only one I am aware of is the ASRock AM1H-ITX. It is not necessarily cheaper than going with another motherboard and soundcard (given the nominal £30 of an AM1 board and the £30 you quote for a soundcard), as the two places I found for it would be around £60. On the plus side, this is the mobo which accepts DC power in as detailed on the ASRock website. This could mean a smaller, quieter and more efficient build. It would however mean additional outlay for a DC brick but it could be a cool experiment.
ASRock mobo site:
http://www.asrock.com/mb/AMD/AM1H-ITX/
Board on Amazon:
http://www.amazon.co.uk/ASROCK-AM1H-.../dp/B00J0DJJ28
Found on Google:
http://www.casetac.com/index.php?rou...BP&language=en
Also saw it going for £56.25 on eBay.