And I thought getting 39-45(I5 750 under-volted + 4350 video on a m-itx board) watts idle out of my media center was good(54-59 with a 5770 video card)....Beats my desktops 144 watts idle.
You may be able to shave a small amount of power savings with a low wattage(250-300, lower if you can find a good one) high efficiency power supply.
You may also save some power by disabling any onboard devices that you do not need on the board. Undervolting may be an option if the board supports it. Make sure all power save options(Speedstep,C1E ect) are on in the bios and windows(balanced or power save).