Seems like a great parts list. A quality PSU and a used rx580 or gtx 1070, and you are set.
Lots of parts have been steadily increasing in cost.
Make sure to get 3200-3600mhz ram.
For the motherboard I would personally wait to see how b550 motherboards are cost wise after release (so close now). But otherwise the b450 of your choice is fine.
For the SSD, the best bang for buck (IMO) is the sn550. I would try to squeeze a 1TB in if you can, since it should be enough to not have to deal with a secondary drive unless there is mass storage, or all games left installed. They are