This is correct, on average the RX 580 is the stronger card. If you need more evidence read up on any one of these, even Tom's benched this and the RX 580 won in a majority of titles:
http://www.trustedreviews.com/amd-radeon-rx-580-review-performance-page-2
http://www.eurogamer.net/articles/digitalfoundry-2017-radeon-rx-580-570-review
http://www.tomshardware.com/reviews/amd-radeon-rx-580-review,5020-3.html
https://www.youtube.com/watch?v=fScs2KH5zVo
http://www.pcgamer.com/radeon-rx-580-review/
http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/75127-amd-rx-580-8gb-performance-review-20.html
http://www.techspot.com/review/1393-radeon-rx-580-vs-geforce-gtx-1060/page8.html
http://techreport.com/review/31754/amd-radeon-rx-580-and-radeon-rx-570-graphics-cards-reviewed/7
I'm guessing that should be enough...
Other than that the above builds look good, but if you go Ryzen i agree with Isokolon on spending more for the faster RAM, it's well worth it on Ryzen. As for the Power Supply... i'd still personally prefer the SeaSonic S12-II but the new Corsair CXM are good quality and a strong competitor for the price. It's not like you will notice a difference between which ever one you get.
See some performance tests here for Ryzen RAM speeds >https://www.eteknix.com/memory-speed-large-impact-ryzen-performance/.