The ambient temperature for the crossfire of 4870 was 21.5C.
The opening for the fan on the front is on the bottom of the case, in between the front pannel and the chassis (there is a 20mm * 240mm gap).
For the number, this is my mistake. It's a HD5970, bi GPU.
Regarding watercooling, yes, you can install a H50 but the objective is to have a small Micro ATX case (23L or less) that fits high end, huge monster, high performing air cooled heatsinks. And the GPU(s) that go with them.