This is the WD External Harddrive I have; http://www.newegg.com/Product/Produc...82E16822144385
It is almost completely silent. The only times I hear it is when it starts up, or when I haven't used it for a while and I use a file that is on it. Also it stays almost completely cool. I don't know how the Media Center or My Book do, but I would just swap that hard drive for the more expensive one, as it probably has better stats and I wouldn't really worry too much about the cooling, as WD does a great job anyway.