It will be compatible but don't take Corsair PSU.
Not long ago it was easy to recommend corsair PSU but nowadays the quality has gone down. \
Go for some Seasonic one or what ever you want just don't regret later
For a 270x Minimum 500w and for 280x minimum 600w power supply is required If I was you I would go for a GTX 760 over a 270x and a GTX 770 over a 280x
But the per $ performance of 280x and 270x is better than the nvidia ones so if money is a second consideration go for Nvidia GTX 770