Presumably, this is for gaming.
A rule of thumb is to budget about 2x the cost of the processor for the graphics card.
For your purposes, you could look at a less expensive I5-9600K. 6 cores is plenty for gaming.
Regardless, I think a i7-9700K is about the same price as a 8700K and will outperform it despite having 8 cores vs. 12 threads.
The 9th gen processors have soldered heat spreaders so they run cooler and will OC better.
For any K suffix processor, you need a good cooler. Noctua is excellent quality, but a downdraft cooler is not very efficient.
The NH-L91 is totally inadequate.
The noctua NH-D15s is as good as it gets.
I think I would defer on the HDD until you actually need the space.
Start with a 500gb Samsung EVO either 2.5" or M.2