Build Advice: 2 vs 3 GTX 1080s

I am considering building a new hashcracking machine with either 2 or 3 GTX 1080 Founder Edition GPUs.
I am not sure if cramming 3 x GTX 1080s into a desktop case will be problematic from a heat (and power) point of view, so may have to look at just 2 GPUs.

The case that I was considering is an NZXT h440, with the drive bays taken out so as to direct more airflow from the front of the case onto the GPUs.
The power supply is comparmentalised off so as to not dump heat into the main case. Would add an extra two fans to the top of the case to help dump heat.

With 2 x GPUs, there a a big space in between the units for airflow. With 3 GPus, not so much.

case: NZXT h440
Motherboard: Gigabyte GA-X99-Designare EX
PSU: Corsair AX1500i
CPU: Intel Core i7 6850K Broadwell-E 3.6GHz
CPU cooler: Noctua or similar (not watercooling)
Any advice regarding the feasibility of 3 x GTX 1080s, vs 2 x GTX 1080s in this setup would be appreciated.  

A second option may be to look at the feasibility of 2 x Titan X (pascals)

u should look for a better fan to, than the defaults one.
couple of weeks ago some one open a post about some problem that he had with his 4 cards if i remmber correctly.
and we suggest him to swap his fan to server ones with higher CPM, u should look into this thread.

the problem with those fans is the noise ..