my list is missing the cooler, the ssd, the keyboard and the mouse. I only had a list of motherboard (not the actual model just chipset so that was a guess on my part), CPU, RAM, and GPU, even then with a 550W power supply you have plenty left for future use/overclocking and the voltages that will require.
the 315W is the total power consumption of all the parts on the list from the PSU, total draw, not idle.
adding another video card will add 150W and you will still be under the 550W PSU limit (465W with 2 GPU's)