I have a very power demanding (450w continuous) computer that I rarely use as a gaming rig anymore, or at all actually - in the mean time I had it on 24 hours a day running desktop ubuntu with web server functionality (apache2, mysql, php, rails 2.0, mail, ftp). This server is intended as a 1 - 5 users concurrent meaning, my blog, s/o blog, and a few friends who read them. The server also provided my xbox 360 with some music (when it worked with ubuntu), video, and a private shoutcast server for me to listen to when at work.

So we are focused here on the hardware and physical size as well as energy efficiency.

Ideally I would like to keep the most important components (for cost savings)- I have a 64bit amd 3200 939pin, 2 gig of ram and 4 hard drives (250gb, 80gb, 40gb, and a 30gb). I could consolodate the 4 to 2 or 3 perhaps.

Ultimatly I would like to have the same functionality in terms of a 'media' and web server however here are my additional goals.

I want this to be physically small, I imagine a small cube.
I want very low continuous power so I can justify keeping this thing on 24 hours a day for just a few small blogs and music streaming.
I also want this pc to run very cool so a: less power consumption by continuous fans, and b: less noise (my current pc is very very noisy).

Additionally, no monitor is required, Ideally (and I do not know if Ubuntu has this capability) I want to be able turn it on and off via a command through the network, and I want to be able to administer the computer completely through the network if possible). Installation I assume a monitor is required so I am only concerned with every day use.

A remote desktop, so gnome probably, I would like but I can manage all command console - ssh - whatever if it keeps resources down.

I would not intend for this thing to be anything other than a server to provide me media and web hosting.

If you are wondering, Yes I could use a blogging site to host my conversation but running my own server for mail, web, ftp - the administration is much more rewarding and i learn alot along the way.

So long story short - do you have any suggestions for a mother board, casing (Would it be best to try to build my own or can I find pre fab very small boxes), upgrades, downgrades, etc?