No, I think the 8700K is the best choice for the price and the performance. It's better than the 9600K, and can be overclocked to be better than the 9700K, and your average frametimes will be better as well thanks to HyperThreading.
I recommend replacing the motherboard with the Gigabyte Z390 AORUS PRO. It has a much better PCB, and the VRM is top-notch.
I don't know anything about the 550W Rosewill CAPSTONE PSUs today. They were at one time a damn good PSU, but today's version is probably crap. I was gone from OCN for about a year, and before I left, they were no longer good or safe to recommend. I recommend the Corsair RM550x because you can get it for $79.99. I can also recommend the 550W SeaSonic FOCUS Plus Gold for $74.99, but with how much better the Corsair RM550x is and with its good price, I won't recommend anything else.
I want that monitor dammit. Argh.