Thanks for the reply.

I'd really like to build one, I like the method "learning by doing" :-) I already have a HTPC but it's getting really old and more and more noisy, so I'm thinking about making a fan-less one.

Could you write some tips about the PSU and other things?

I've been thinking about the J1800 motherboard (http://www.tomshardware.com/news/gigabyte-ga-j1800-d2h-motherboard-celeron,25942.html ) which has integrated a dual core Celeron processor.

The HDDs - I'm thinking about an SSD or a WD Green, but a 2.5" HDD could be better indeed. RAM - no idea which RAM I would use.

And I have absolutely NO idea about the other components :-)

Can I ask what pre-made did you buy if it's not secret?