Thinking about upgrading GTX 650 video card to a Zotac GTX 760. But I understand card wants a minimum of 500W PSU with 30A. My present PSU is a Antec vp-450 450W with 2 18A 12V rails (36A in total?). Not too much in my rig. One sata HD, one dvd burner, one case fan, one sound card, I5 2500 (not...