I'm not a thermodynamics engineer, but one thing that strikes me as odd about all of these is that most of the fans are sitting parallel to the motherboard, and

I'm not a thermodynamics engineer, but one thing that strikes me as odd about all of these is that most of the fans are sitting parallel to the motherboard, and sandwiched between the board and the wall (which only has small holes). Whereas the Apple way, since the PowerMac G5, has been to mount the fans perpendicular to the motherboard and daughterboards, and push air across them. That seems like it would be much more efficient, better for both cooling and noise. Is there a reason these PC systems mount the fans that way? Is it not actually as inefficient as it seems? Is this a case of modular parts each needing their own built-in cooling, and not being able to look at the bigger picture?