1000w PSU is plenty for just about any gaming card, average requirement is 650w PSU but it depends on the actual card model. Some dual cards running together using Crossfire require 1000w (manufacturer's recommendation).
However Delta is not exactly top-notch, but neither is it rubbish. Best PSU brands are Seasonic, Corsair, and CoolerMaster. but it's your call as to whether or not to stick with the Delta one.