If your power adapters do have two 4pin molex connector to one 6pin connector then that is a lot better. However does your PSU have 4 cable harnesses with those 4 pin molex connectors? Because if you don't take the power from different lines it is no better

Did you down clock the ram while mining? It saves a few watts.
My PSU has this dreaded OCP and if I don't start my cards one by one it trips every time. It even trips if, while mining, my CPU goes under heavy load for some time. According to kill-a-watt I should still have over 100w of headroom but these processing spikes can draw a lot of current when they occur. So while PSUs should be able to produce the power they are rated for YMMV.
What's the make and model of your current PSU?