Low power consumption appliance based on desktop computer

I would like to have an always on server for my home network, and altrough I have already two ARM based routers which can be customized, I would like to have an x86 based computer, because it is much easier to install linux programs on it and normally they have faster processors and more memory than the ARM counterparts.

I would like to use it for 3 functions:

1. To be the center of the home network with an Apache based WEB interface, whcih can do all network related tasks
2. Install an Asterisk PBX and connect all our phones to it, including mobile phones via Bluetooth
3. Be a storage backup server with two Tbyte or close to Tbyte SATA hard disks

Earlier I had a 3G/HSDPA WLAN gateway created from an old laptop, and with the HDD and display switched off, it consumed only 10W, but I was considering to have a modern desktop motherboard with a Intel E2160 or simmilar processor to reach a good power consumption.
Before going into this I checked the power consumption of different solutions on the internet and it turned out that even with an Atom processor based desktop solution it is very difficult to go below 30 W which is not acceptable for my purpose.
Here are the figures I have found:
Gigabyte GA-MA74GM-S2 with AMD processor - 31W - laptop HDD
Atom 230 single core - 27W - with laptop HDD
Atom 330 dual core - 41W - with desktop HDD
Gigabyte G33M-DS2R with Intel E2140 underclocked 40W - ??? HDD
So the conclution is that even the very low consumption of the Atom processor itself is nut visible on a complete system, as other components determine the total power consumption of the whole system.
When exploring this I found a very good site about building mini PCs here.
And found a far east company with a big selection of complete mini PCs on amazing prices here.