Just one thing to add to the post provided by n0ns3ns3! ^_^ With that GPU there is a chance you may cut it fine with the amount of power delivered by your PSU. the 1080 is rated up to 250 Watts as I recall, and it can hit that when it is operating to its fullest. If you find you have some random crashes, or a hang, consider upgrading your PSU.
I just mention this because while the PSU may have the connectors to deliver for a 1080, you haven't mentioned the other components, drives, CPU, etc... that are in the machine. Take it easy ^^