i have an i7 6700k running at 4.3 ,32gb ddr4 ,2 ssd 500gb, 3 sata hdisks and a gigabyte gtx 1080 (not ti ).i want to change my power supply cause its old and an overkill ,but i am not sure about the watts.Also i might pick another gtx 1080 for sli,not sure yet.So, my question is ,first , how...