I've got a few questions for the gurus 😉 I am looking to upgrade my current motherboard/cpu from x99 (rampage v edition 10 and 6850k) to x299 or z390. I will be reusing my Corsair Dominator Platinum 32 GB (4 x 8 GB) DDR4-2400) [CMD32GX4M4B2400C10] memory, SLI 1080s, HDD and 3 SSDS, and 1 NVME pcie ssd. my current configuration I have my gpus (16x/16x) and pcie ssd at (4x). My question comes into regards of what socket to upgrade to.. keeping in mind the parts I will be reusing~ I use my PC mainly for gaming, some streaming, and graphic design. I've put together a few items I have been comparing, now I am in need of some feedback. X299 it seems the omega was the board but now there is a newer what seems to be better choice. or should I just go the z390 route but that will lose quad channel support among the much needed lanes for SLI and NVME drive. .. or will that 9900K and Mobo suffice? here is what I have so far.

i9-9820x and ASUS ROG RAMPAGE VI EXTRME OMEGA. ($1,479.97)
https://www.newegg.com/core-i9-x-series-intel-core-i9-9820x/p/N82E16819117332
https://www.newegg.com/asus-rog-rampage-vi-extrme-omega/p/N82E16813119187

newer and cheaper Strix gaming II motherboard (https://www.newegg.com/asus-rog-strix-x299-e-gaming-ii/p/N82E16813119215)

or

i9-9900k and ASUS ROG Maximus XI Extreme. ($1,416.97)
https://www.newegg.com/core-i9-9th-gen-intel-core-i9-9900k/p/N82E16819117957
https://www.newegg.com/asus-rog-maximus-xi-extreme/p/N82E16813119168

From the benchmarks and reviews I have been able to find they seem closely comparable, and right now being nearly the same price point. ... what to do what to do!? I am also running a custom loop.. so cooling shouldn't be too much of an issue~ prices above include a EK-Velocity RGB - Nickel + Plexi cpu cooler. (https://www.newegg.com/p/37B-000B-00237)

thoughts... suggestions, thanks in advance!