I just got a system. I got a great deal on Newegg. $999 shipped no taxes. Here's the link, although not available anymore, you can see the specs.
https://www.newegg.com/Product/Product.aspx?Item=N82E16883102462
I liked the PC because ram and GPU prices are inflated. I went looking for the best possible CPU and MOBO combination in my price point. That is how I ended up with the i7-8700k and the z370ftw mobo. Both are just about the best you can buy without just wasting money. 8gb of RAM and the the 1060 6gb are sufficient for most things.
I have been looking at a few upgrades already however so I opened my case and can give you the exact specs...
https://pcpartpicker.com/list/#incompatibilities
This is the exact system I have ***EXCEPT*** the Samsung 970 Pro m.2 2280 NVME SSD and the 16GB of ddr4 2400 RAM. Those are my possible upgrades. I have been doing a little reading about if I can put 16gb of the exact same RAM with the existing 8GB since the price of 16GB is a better value and the 8GB.
The system works very well. The optane lets my OS boot from a traditional HDD in about 9 seconds. However, many things run slower than I would like. Considering you are building the system from the base, I wouldn't go with the optane + HDD solution. Know that the Optane m.2 combined with the Samsung 970 eats up 4 of my 6 Sata lanes. Yes, 1 m.2 shuts down 2 sata lanes.
RAM is sufficient for me but 16gb would be much nicer since you are DIY. Get 2x8 of something you know that you can later get 2 more of the exact same 2x8. I'm not sure of the true benefits of buying the faster Ram. From what I have read faster ram is the least of the performance/dollar investments.
I think you are selling yourself short on that SSD. Yes it is a SSD but the SSD is limited by the Sata port. Also that is nothing in the way of memory. Modern games are about 80gb. You have enough SSD there for you OS and one game. I am not expert on computers but I believe you will be happier if you invest is a NVME SSD of 500gb. Yes your price will go up by $100 for something like the Samsung 970 EVO but it will likely be money well spent.
I have Xbox One 1tb, and a 5tb external HDD. Crazy how fast modern games fill it up. I can post the sizes if you would like me too. I think games like GTA5, Battlefield 4, COD WW2, etc are about 80gb each. Xbox Play anywhere is something that I am going to be using my PC for. Forza Horizon 4 is going to look much better on my 3440x1440 100hz monitor than it will on my 65" 4K.