First of all, 1300w PSU would be sufficient if you have enough cables. Buying expensive PSU - pointless, buying oversized PSU - pointless. You have to take into consideration only 2 things. Your system power draw is around 100% of PSU power rating or below and PSU is gold rated or above. That is it.
All those comments - get expensive PSU, get 2x1000w or what ever other wattage PSU are complete BS and are factless. Period. I got couple of 8 gpus (gtx 1070) rigs running with SINGLE 1000w gold rated PSU! Stable! First of all, to all people giving those random things like unstable, reduced lifetime etc I would suggest go and study little bit of structure of PSU and how they work.
Most of normal PSU have 5 or more year warranty, meaning you can run them straight at 100% load of at least 5 years! End of the story.
One I am using is Enermax Revolution 87+ 1000W PSU that have 4 12V 30A power rails. Quick calculation P=IV=1440W + sata cables that supply part of power to GPUs trough powered risers are on different rail thus there is even more total wattage supplied by PSU. And that is just amount it have to reach to have Over Current Protection (OCP) kick in. This is reason I would suggest using multi rail PSU if you require more then 500-650W - extra safety as if you have everything on one rail that have OCP, lets say 100A, then most of your equipment will burn out until OCP trips and switches off PSU.
Most of PSU manufacturers will state total wattage produced from 12V rail while there are 5V and 3.3V rails that supply mobo, sata, etc that are not included and alone are extra 100-150W.
Oh and in all my years working as electronics engineer, we design things capable of working way above values specified to customers!
Currently I am building 8 GPU rigs with 2x750W Chieftec gold rated PSU just because it cost less then getting single 1000w-1300w.