that is just cool. Having done some fun noise cancellation tests in college I wonder how/if they managed to make this effective at all. The thing with noise cancellation headphones is that it is canceling the noise at a choke point (your ear canal) which is an environment relatively easy to control. The issue we found with more general noise cancellation is that in an open environment you have to try and match the position of the source of the noise, or place it in a spot where there is a standing wave. If you put it anywhere else then you end up with what is essentially a moire pattern of hot and dead spots in the room.
The big issue I see is that every case is different, the size and layout of the hardware inside the case is different, the airflow through the case is different, and the room and location in the room that the box sits in is going to be different. Not saying it is impossible... just that it would be very difficult to come up with a design that can negate that many variables, and more difficult to believe that it would silence the CPU block further than what their already nearly silent fans do.