I want to upgrade my GPU, but my PSU (Seasonic S12-II 520W) only has 1x8-pin and 1x6-pin. I have a spare PSU lying around- an Antec VP550P- and that one does have 2x8-pin connectors. According to the PSU tier list, the Seasonic is a higher-quality unit, but I'm not going to do any OCing. Should...