Relative to their poor performance, the Atom systems seem to use a lot of power. Since Atom CPUs use very little...
The power draw of the motherboard, chipset, and cpu needs to be less than 40 watts. With drives that brings the budget up to 45-50 watts on a 60W digital power supply (the display is a separate power issue). I don't think I'll have access to any spares but the laptops I have are 65-85 watts which, although low, are not low enough. CULV systems that I've seen don't have that much of an advantage for the money and Core 2 Duo Mobile chips are $250-$350 if you can get them.
But thanks, a system with a e3200/e3300 seems like it could work. The X-bits Lab piece
(http://www.xbitlabs.com/articles/cpu/print/celeron-e3300.html) does say that a 50W system is possible with integrated graphics (which is what I'm using). But what confuses me is this - it lists the e3300 with a TDP of 65W. What does TDP really mean and then how can you get an idea about how much power a system will consume? How can you tell which is lower: the e2200, e3200/3300, or a e5200 if they're all rated 65 TDP?