most pc components can withstand extremely low temperatures for short amount of times, ie LN on the CPU/GPU. The usual parts to cause trouble in the cold are optical drives, hard drives and possibly displays.
If anything, you might be limited more by the PSU than anything else in your build.
Thanks for the comments, guys. Higher capacity PSUs are an option, but they get a little pricy from 200w out. As far as performance, the most it will do is playback SD video, capture video from a webcam (15 fps low res stuff.) I don't see any reason draw from a system for this purpose will be very high. -- I'll revisit the topic once I have a more solid part list in mind.
Anyone have working experience with LCD's in low temps? maybe there are some variables we can look at there.