Quad 1080ti Workstation

Hello after reading some post, i found some things, im gonna post here cause  i want to go for quad 1080ti, i will start buying all unless all GPU and i would add periodicaly(like 2-3months) each 1080ti , in like 8-10) months i could have done.

Motherboard: Asus X99E WS
CPU: i7 5930k
Tower:Big Tower EATX case
PSU: 1500W PSU
Samsumg Evo 860 500GB


And about the cooler, what is better fan or liquid refrigeration?