Sorry for the late reply, I forgot my password for pcpp. The cooler is great it makes over locking a breeze, it looks nice, and is fairly quiet. I have never used the bequiet dark rock pro 4, so I wouldn't know.
Actually this is not the most expensive build, because the 11 8TB drives that he has in the part list are not in the build. this is proven because he says he didn't want any HDD in the build.
Nice build! Imo tho I would recommend getting faster ram, if you sink like $25 more you could get 3200 MHz ez. Also, for the amount you got the RX 580 for, you could get a cheaper 590 for that price.