I'd save on the mobo and buy a b450 tomahawk, it's abt 100$ less and supports 3rd gen ryzen.
Buy the 1660ti Since the RTX series are still in an infant state and also an expensive one, the rx5700 has problems with gen4 from what i've seen so wait til amd fixes it.
The RAM frequency speeds are good if you go for the x570 but if you go for a b450 due to budget reasons u better go for a 3200 one
Pick up the 650w PSU, gen4 mobos seem to suck a lot of juice.