It was already explained to you with numbers why that's wrong. You're welcome to size your PSU however you see fit, but "most of the time" is not the important metric in sizing a power supply.
Let's try a saner, based-in-reality-and-safety estimate.
We have to account for:
Base system (MT-C224 mainboard 15 watts, CPU 80 watts, memory 2 x 6 watts) -107 watts, peak consumption.
Fans - 15-30 watts.
Drives - 8 watts times 6 drives. This is idle current, NOT spinup current, and it is definitely additive ON TOP of the spinup. Which is ~144 watts, but could trend a bit higher.
That's 329 watts right there. However, you need to account for the fact that you shouldn't be peaking out a power supply, regardless of what the marketing glossies say. A 360 watt supply should never be asked to give more than 80% of its rated power, or around 290 watts.
Now, what marbus90 is going to say is that "oh but that's okay, see, even jgreco says 329 < 360". As an engineer, I solidly believe in
derating of electronic assemblies, because we know that if you drive something all the way to spec, it is more likely to develop faults, and as an assembly is in use for years and it ages, its ability to sustain its rated spec may decline somewhat as well. So I really like to see the math that shows the system isn't likely to draw more than 80%. This also gives a lot of elbow room if someone plugs in a faulty USB device, or a fan seizes up, or something else bad happens, or when you need to temporarily attach some other drives for data migration purposes.
But, the truth is that the 360 is *probably* going to be okay, even though peak potential current is over 80%.
However, there's really not much of a penalty to go with the 450 instead and be much more solidly in the comfort zone. You're attaching over a thousand dollars worth of electronics to the thing. Why take a chance?
That comes from my experience building these things professionally. I like the headroom and I don't like to blindly trust that Seasonic has actually built in sufficient capacity to cope.
So anyways, as you can see, marbus90 and I have a disagreement about the definition of "overpowered." You're free to analyze my explanation and either accept or discount it. I've shown my math and my reasoning.