Silent drive enclosures

I have need for .5-2 terrabytes of storage that is silent. I have a drive right now on my media machine that is a 500GB drive - but it has the noisiest fan in the world that pretty much comes on whenever there's any drive activity. Since I need to think about updaging capacity soon, I wanted to start looking at drives that would be, well, quieter.

Bonus points for low power, the intelligence to shut down when the host machine shuts off/goes to sleep, etc...