not just a media server
the key is that it can be more than just a media server and still take up very little room and be ultra reliable.
I have a 2008 mac mini - 2ghz core 2 duo. it cost 250 quid 'new old stock' from an ebay seller.
In 2010 it replaced a previous 2006 mac mini doing the same job.
It sits on top of 4TB of iomega storage (looks like 2 thinner mac minis)
the whole thing runs 24x7 and has done for the last 2 years.
it serves ATP and SMB shares to all other devices around the house, the runs evocam with 5 IP camera 24/7 as home security, it runs usenet and torrent downloads. It even acts as a node for rendering when required.
it does all this making hardly any noise, using very little power day in day out - gigabit ethernet - what more do you need ?
Maybe I'm unusual but I quickly realised a 'media server' was a waste of space - it had to do more to be useful. So it replaced by file servers, then I realised that with a BT keyboard and mouse I actually spent at least 50% of the time using it as a computer - to surf the net, do emails, reply to forums (like now) - so having something like XBMC (which up to 2006 was my solution - I had 4 XBOXes throughout the house running XBMC, getting media from a central server) just wasn't enough.
This 250 quid core 2 duo plays everything I throw at it (mostly now through VNC or Movist, but XBMC is still used occasionally) - inc 1080p 5.1 etc, etc.