Alright, new motherboard is in the computer now and everything is up and running as it should be. Hybrid sli is enabled and working amazingly well. I ended up changing some things and pulled out one of the two hard drives I had. All in all, idle consumption is down to 58W, and at the click of a button I can power up the video card to do any 3d stuff I need to.

There is still tweaking to be done. I didn't play with anything yet since I knew a new motherboard was going in and I might have to reinstall vista (which I did). So, now I'll start looking for ways to further tweak the system. Unfortunately, there arent any 64 bit vista drivers AMD's cool'n quiet. This technology dynamically steps down or up your CPU speed based upon how much processing power you need.

Well, a little more digging revealed that vista has cool'n'quiet drivers imbedded in it already. So, it is working and it is stepping down the cpu speed and voltage. Yay. I'll probably still do some tweaking with power settings, but I'm not sure how much it'll effect things.

It's a bit late...
The solid state drives have already been mentioned.
But for quiet and low energy consumption, have a look a water cooling. The radiator sits outside the box and can use a large (relatively speaking) fan with low rpm.

Have you guys looked at the FitPC2 yet? That's a pretty neat mini computer. Uses roughly 10 watts and supports HD Video.

Got a link cholcombe?

Yep, right here Fit PC 2

From what I saw their computers are running an intel atom chip instead of an arm like most small systems do now.

If you're looking for another PC to use for basic office work, web browsing, and multimedia, check out the Beagleboard.
BeagleBoard.org - default

That fit pc 2 is quite a nice little package. It seems somewhat decently priced too.

The beagleboard is pretty cool too and quite cheap.

I recentli bought a Mac mini and a 23inch LCD. Idle power usage is 30W (13W for the Mac and 17W for the monitor). I did look at laptops for even better usage but screens are just too small - besides, I already have a laptop. You can also install Windows or Linux via Bootcamp on the Mac if you really need to.

I recently came across this page:
VIA EPIA Mini-ITX motherboard...
...or My Quest for a Quiet Computer
It's more about reducing noise than power consumption, but the two usually go hand-in-hand. It's about a low-power motherboard.