I just saw this by a guy on a DIY forum: http://internetofmusic.nl/home/

It's a Pi with DAC (might be Hifibury+?) and a 2 channel, 30W Class-D Hypex amplifier in one box, ready to go with wifi and your choice of software, shown here with the case open. Looks to be priced at about £210 + VAT . Doing a quick parts add up with estimations on the case and bits, that works out to about £50 or so for someone to build and set it all up for you - not bad at all :