The psu wattage you need is determined by your graphic configuration.
Here is a handy chart.
http://www.realhardtechx.com/index_archivos/Page362.htm
GTX1080 is about 520w.
I have no problem overprovisioning a PSU a bit. Say 20%.
It will allow for a stronger future graphics card upgrade.
It will run cooler, quieter, and more efficiently in the middle third of it's range.
A PSU will only use the wattage demanded of it, regardless of it's max capability.
Of more importance is the quality.
Pick a tier 1 or 2 unit from a tier list such as this:
Credit to @Starelementpokeand @Energycore for helping out with this long-awaited refresh of the old PSU tier list by Aniallation (who previously went several months without logging in), leaving the old list in need of help. This is simply an update of the list that was flawed in creation by the P...
linustechtips.com
The Seasonic focus 650w listed above ticks off all requirements; a very good unit.
Plus, it is compact, only 140mm long.