You might want to avoid EVGA GTX 1070s, as many have reported overheating issues with them. EVGA is supplying thermal heat pads to those who request them. (Despite the foregoing,EVGA maintains that under normal operating conditions there is no overheating issue.) Are you sure 550 W is sufficient? The minimum recommended power for a single 1070 is 500W. Or are you adding the 550W in addition to your current PSU?