if it was me, i would probably put a custom water loop in it. i checked the dimensions of a similar box and looks like there is just enough room to put a 240mm x 120mm radiator in the bottom (leaves just under 3 inches for the motherboard and its mount). have the fans blowing out of the bottom and attach some feet to the bottom, just enough to let the air escape. i think watercooling is a good option for small builds, as long as they can support it. it would greatly reduce the amount of air flow required since all of the heat exchange, as far as cooling, is occurring in one place - at the radiator.
as long as you're not tossing it in your trunk and driving through the woods, i dont see it being an issue as far as springing leaks from...