I increased the size to a 24"x24" square. This gives plenty of room I believe.
The power switch/reset/usb panel stuff can go above the 5.25 (dvd image is used as a scaled place holder)
Green cubes are the HDD caddys.
If I put the 5.25 under the front radiator it will be much taller by several inches. I think that it will be better to have the 5.25 on the side, then you can put the power switch and usbs above it or below it.
The other space efficient thing is to rotate the 5.25 90 degrees and tuck it to the left or right of the radiator. This would make the wiring for it much easier.
I have three questions:
-What side of the desk will you have the case on?
-What are the pump dimensions (rough cube please just like the HDD caddy)?
-Do you like either of the designs above with the 5.25 placement and if so which one?
Position on desk could determine which side I put the 5.25 and switches.
A side benefit of not putting the 5.25 under the radiator is you will not have to reach as far if you have this to the left or right of your monitor.
So if you put this to the right of your monitor then I should put the switches and 5.25 on the left side of the case.
I also need to know if pump will fit next to the power supply (I think it will but would like to have a scaled model of it)
I think the straight flow through design of the radiators will result in very good temperatures. You could add ducting for the radiators too.