I kinda agree with CarolinaSock. If you're going with the B450 chipset, you might as well go with the Ryzen 5 3600. It costs slightly less but has better single core performance (important for gaming) while still being a multithreaded CPU for non-gaming functions.
There's no reason to pay that much for RAM unless its purely aesthetic and that RAM kit comes with two dummy DIMMS. I mean, here's the same capactity, same clock speed, and same CAS latency for $30 less https://www.newegg.com/g-skill-16gb-288-pin-ddr4-sdram/p/N82E16820232181?m_ver=0
You can probably save a bit more with another SSD, but that's entirely understandable if you stick with Samsung. Their SATA SSDs do tend to outperform all others, but in essence you're paying about 30-40% more for about a 10-15% improvement. I'd just highly recommend a drive with a DRAM cache if you're going to be using it as both an OS drive and a storage drive. Crucial MX500, Adata SU800, WD Blue are good alternatives. Again, the Samsung drive will outperform all of these - I'm only making the recommendation for costs.
The 1660Ti is a good card. It's decidedly better than the RX580, but.... it's also still in the same mid-range class as the RX580. You aren't exactly "moving up" - it's more like a better lateral movement. I agree with CarolinaSock here too and would recommend any of the GPUs he mentioned.