I wondering if anybody's made a small but reasonably-fast hackintosh?
I was considering trying to stuff my hackintosh in something like this Silverstone LC19...

But it's so thin you need Silverstone's special low profile CPU cooler. It's the ideal case for building a mac-mini hack though.
Instead, I think I'm going with this Moneual 312...
It's about as slim and compact as I can go with my Mini-ATX and quad-core setup.

I think if you can get an aftermarket cooler on there (such as a Nexus Low 7000 or Skythe Shurekin low profile) it will not be any noiser than a nice silent PC.