I know excessive heat is bad for components, but what about cold? I have a shelf near my built-in air conditioning unit. It gets my Onkyo receiver quite cold. I also have a PS3 and 360 (which could use all the cold air it can get, LOL). Is that anything to worry about?

Shouldn't matter. But here's a tip, if frost starts to form on your xbox, it's prolly a good idea to turn off the ac :-)

The temp is not an issue. The cooler the better. Just be careful with condensation. That will kill any electronic device.