I would probably go for RAM with higher frequency than 2133MHz as this will slightly improve performance.
What Nightlord01 said + better graphic adapter is much better investment for the money. As for the various SSDs, in most cases it is much the same as with the RAM. I have read from computer magazine an extensive test of the various SSDs and the time it takes between fastest and slowest SSDs to load up Windows is only 3 seconds. So: cheap RAM & SSD and direct the saved money for graphic adapter.
You're lucky to get Core i7-8700. I wanted to have that by the Christmas, but all of those have pretty much been sold out in Finland. So i7-7700 it is to go with GeForce GTX 1080 Ti. Computer store is gathering the parts and they have promised the machine & peripherals to be ready in couple of weeks. Total sum (including assembly, 144 Hz monitor, 3 controllers, speakers, headset, and HTC Vive) so far is 4566,10 €. At first they offered me m.2 SSD for 499 €, but after flipping through my computer mags, I e-mailed them to get SATA version instead and I saved 150 € with that.
[edit]
I included list of the parts on PDF-file. 90 € is assembly fee and list is missing Kingston HyperX Cloud II headset which cost 99,90 €. Also they may shave off some of the price. I hope.