Looks ok, you could probably save a little on a Ryzen 2600/2600X which might offer a better overall system but would game much the same.
Also you don't really need a $90 cooler for an 8400, for the price of that CPU & cooler you could almost get a non K i7 8700 and just use the stock cooler, might run a little hot but would still be a better option for the price. Some reviews have suggested the 8400 throttles a bit with stock cooling, but it doesn't overclock so something cheaper would be fine.