Do you mean a PC where you will watch movies, or a PC that will be on a LAN and will store movies for watching from other PCs?
I suspect something based on a 780G (or 790GX) motherboard and Corsair 450VX would be a good start. That is, it will be quiet and power efficient all right if you don't need to buy a video card at all.
I like the WD6401AALS disk a lot, but in your case it's probably worth going with the WD 640GB Green because it's quieter and consumes less, and the lower speed won't matter at all for playing movies.
The Antec P182 is a great case if you can afford the money and want a quiet PC.
Im looking to cut my satellite bill and replace it with faster internet, then stream media through the quiet, efficient box both for viewing on our main TV and other PCs. Therefore it will kind of need to be able to both store and be able to watch off.
Ill take a look into those products and would love to hear any other suggestions.
Tomshardware built a low power consumption pc based on an e7200/ g31 mb . Total power draw was around 75 watts
The AMD 780 is great onboard gfx but the chips are hungrier and I doubt it can compete .
Im not sure if the e7200 is available any longer but the e7300 is much the same .
You could even underclock the cpu . It should throttle back in most BIOS to a multiplier of 6 which would reduce the speed and power usage about 40% . Maybe more if you undervolt it too .
Add a WD green hard drive , 4 gig of RAM , turn the case fans to low if you have the antec case and it would sit three 24/7 using half the power of a light bulb
and then get a cheap GPU; http://www.newegg.com/Product/Product.aspx?Item=N82E168...
But then you would need to power the GPU, which would probably end up consuming more power, but you would have better video handling and playback with the discrete gpu...Depends what your priorities are I guess, you would get more performance out of the intel build though.
Heh found it...
So according to this site, the max power draw of a reference 4670 card is 59w, and since you don't have a fan on that card, it will be less, and you probably won't max out the card either just watching movies, so its consumption would probably be around 30-40w I would guess. http://www.gpureview.com/Radeon-HD-4670-card-579.html