Seasonic

Can anybody identify this connector attached with this second hand Seasonic PSU I got: https://imgur.com/a/5ps0o Seller said it came with this 24pin cable but I'm wondering what its for and why it didn't come with a black one because I got the KM3 variant. I'm suspecting its a Japan version but...

I have selected these parts for my gaming pc, I am really not sure about the watts i want for power supply ? All suggestion are welcomes and kindly tell the things I need to keep an eye out for : [PCPartPicker part list](http://au.pcpartpicker.com/p/syn423) / [Price breakdown by...