Work watts/amps into your formula
Just did a quick build for $1100 and it suggests a video card with more power requirements than the PSU can provide. The direct link for the video card shows a minimum of 600 W with 42 Amps on a single +12 Volt rail. At 80+ Certified, the 620 W PSU would not have nearly enough power.
LOVE this site though, this is really awesome.
Actually if you are reading the manufacturers specifications, they massively overrate the requirements to make sure that you don’t put a ton of peripherals on and complain at them.
Also, efficiency doesn’t take away from the rated wattage as the rating is DC power, not AC. The 620W PSU will draw more than 620W from the wall.
620W will be plenty!