You've got the conversion backwards there. a 380w power supply that operates at 69% efficiency delivers a full 380w(assuming that's an actual capacity rating, instead of the skewed numbers that Power supply manufacturers use) to the PC components. What the efficiency means is that if you're using the full 380w on the PC side, that the power supply has to actually draw 551w from the AC outlet, and that then 31%(100-69) is lost to heat/waste in the conversion process from AC to DC.
Those numbers in the review are on the AC side though, so like with that particular power supply, at 69%, the 263w at AC side means the PSU is actually only outputting 181.47w to the variuos components in the PC.
now whether your PSU in particular can handle this depends on the wattage on each particular rail.
You are about to answer a thread that has been inactive for more than 6 months. If you still wish to proceed, please ensure that your posting is original and does not duplicate or overlap any prior responses to this thread.