RAM/MoBo/CPU Compatibility Question

Solution
you're fine.

in the begining x99 was the only way to use ddr4 ram. but the new 170 chipset brings it to the mainstream. enjoy the new build
no problem.

as a side note, if you go back to the partpicker list, you may notice the "compatibility check" just above the list itself. the site already does a quick check for you and will let you know if it things anything won't work together. another nice little addition to the service they offer. :)