farhanorakzai :
Should I just use my Hx 650 then? The system has an i7 3960x, rampage iv extreme, gtx 780, 24 gb ram, 1 hdd, 2 ssd. Is 650w enough?
Use the pinouts at the link I suggected to figure out what voltages go where (Ground, 12V, 3.3 and 5V.)
Then just move the pins on the HX cables at the PSU terminus to match the Seasonic.
Alternatively- take a voltmeter and measure the voltages at the PSU modular connection. Then move the cable pins to the appropriate spots.
Pin 1 on the SATA cables is the side with the notch. That is 3.3V, followed by ground, 5V, ground, and 12V as below.