Here's an idea I had. It's not really feasible since the heat sinks aren't readily available and would be crazy stupid to custom make. It was fun to put it together in Sketchup though.

What if you could make a heatsink like this?


They would fit together with the Klondike 16 board on the back, like this:

Notice how the pin placement is more dense towards one end of the heat sink.

When you put four together, they create a tunnel:


Less dense end. This is where you blow air in:


Dense end. This is where you want the air to come out:


Now, since there are more pins towards one end of the tunnel, more heat will be given off in the denser end. Thus, the board temperature is the same in both ends.

So, make a case of plexiglass boards and some screws/rods:


Put some fans and feet on, and you are good to go:


Those are two 140mm fans, which will ensure good airflow both inside the heat sink tunnel and over the top of the boards. Air is sucked in at the bottom, and pushed out on top, working with the natural flow of hot air.

Voilla! The K64 cube.

So, the heatsink I made up for this design is, as I said, not feasible. However, it would be possible to use the same tunnel design with a normal heatsink - but the chips towards the top of the cube would get a little warmer than the chips on the bottom.

The cubes could be arranged in a square at least 2x2 for a 256W space heater.

k16 is too big (100x100) and heatsink is max 50x50:

http://www.fischerelektronik.de/web_fischer/de_DE/K%C3%BChlk%C3%B6rper/D02/Miniaturl%C3%BCfteraggregate/PR/LAM5_/index.xhtml

or sub-optimal solution:

http://www.fischerelektronik.de/web_fischer/de_DE/K%C3%BChlk%C3%B6rper/D04/L%C3%BCfteraggregate%20mit%20Axiall%C3%BCfter/PR/LA5_/index.xhtml