Long story short, I did XMP first.. failed. Since I've modified the secondary timings to match what is in the SPD of the DIMMs. That also failed, so I've tweaked VCCIO and VCCSA mostly. All this has gotten me to 2800.
I'm currently testing 2 DIMMs and running 3600 with much tighter timings than XMP, but I still can't POST at anything higher.
Edit: I should note that I'm not using the preferred 2 slots for my current testing or I'd have to remove my PITA heatsink again, and therefore cry. I'm not sure how much that is hurting my 16GB experiment.
What are you setting for VCCSA and VCCIO?
A ballpark voltage would be 1.10v for both.
Only enter the primary timings for the Ram and set VDIMM to 1.35v.
Kabylake IMC should easily do 3200mhz atleast.
If you are running tighter than XMP, then you'll need more VCCIO/SA and VDIMM.
What is the RAM kit?
I run 2x8Gb 3000mhz 14-14-14-35 2N with 1.05v VCCSA/IO, 1.35v VDIMM. 4.9Ghz core clock.
I don't plan on going above 4.5 ghz. My unit now is at 4.4.
A lot of stuff there is just people's recommendations. Honestly I am going for looks as well as keeping things practical and compatible too.
As for storage. I'm going to use my current SSD as a secondary. And my secondary now will be my third. I also have a bunch of external drives. If I need more space then I'll just get one of those 8TB WD books. Honestly I don't need another drive right now so I think I'm just going to delete that 5TB.
People can still keep recommending me stuff. I have until next Friday until I buy everything.
Getting 4.5Ghz is garunteed. The worst chips will do 4.8Ghz. The stock single core turbo is 4.4ghz. Stock all core turbo is 4.2Ghz, so all core 4.5ghz is very minor overclock. Should be ok with the limited CPU cooling.
I would go with a mainstream Asus board in the $150 range.
Personally I prefer all my storage to be internal, but that's totally up to you. 3Tb drives are quite a sweet spot for price to GB.
Bump up the SSD as much as you can with left over budget.