Congrats on the x299 Dark 

Intel i9 9900K --->uses Dual Channel RAM ---> Buy the Intel OC insurance --> or if you run faster than stock (DDR4-2666) & smoke the CPU

https://click.intel.com/tuningplan/
 
Performance .. RAM ... run the Fastest "Class" & lowest latency ... for Best performance
 
Check EVGA "Tested" RAM ... CPU and Memory Support
 
G.Skill also has a MB / RAM checker ..... these are Combos the G.Skill has Tested  https://gskill.com/configurator


 
G.Skill & EVGA X299 Dark RAM 

https://gskill.com/faq   
 
 
 
Read these Threads:

RAM Explained

Thread by  GGTV-Jon     DDR4 Memory - Speed versus Timings
 



Articles:
Techspot - DDR4 @ 4000 does it make a difference
good read
 
  What Are Memory Timings? CAS Latency, tRCD, tRP, & tRAS (Pt 1)
 
 
http://www.anandtech.com/...sair-adata-and-crucial
 
 
Web Search:   memory scaling on x299  (x299 can be replaced with a different chipset - if your interested )

What power supply mates well with x299 DARK requiring a 24 pin hook up (not 20 + 4 )  and EVGA GeForce RTX 2080 SUPER FTW3 HYBRID GAMING, 08G-P4-3288-KR, 8GB GDDR6, RGB LED Logo, iCX2 Technology, Metal Backplate ?  
 
Because of the video card 08G-P4-3288-KR a second power source wire from the power supply is required?

For a Single GPU - I would buy the EVGA 1200W P2  1200 Watts
 
They are great PSU I have several
 
If your going to go crazy in OC or multiple GPU at a later date 1600 P2 or T2 1600 Watts
(I have these also - been very happy)
 
On a Tight budget ... 1000W P2 or T2 --> is the min I would recommend for that MB setup... depends How hard your going to lean on it OC CPU & GPU --> you would Need to calculate the Load. 

850W PSU  May be OK ... too close for me to recommend.  I believe in the Rule of thumb 100% of anticipated Load should Not Exceed 80% of PSU capacity
 
Save 10% from EVGA.com with anyone's  Associates Code on your PSU purchase
 

donbrownz
What power supply mates well with x299 DARK requiring a 24 pin hook up (not 20 + 4 )  and EVGA GeForce RTX 2080 SUPER FTW3 HYBRID GAMING, 08G-P4-3288-KR, 8GB GDDR6, RGB LED Logo, iCX2 Technology, Metal Backplate ?  
 
Because of the video card 08G-P4-3288-KR a second power source wire from the power supply is required?

Yes - Run two separate PCIe power cords from PSU to the GPU

The i9 9900K does not work with the X299 motherboard. That is a 1151 socket CPU and the X299 motherboard is 2066 socket.
 
Processors that are compatible with X299
https://www.intel.com/content/www/us/en/products/processors/core/x-series.html
 
The recommended PSU's are solid, EVGA's G3, P2 and T2 line-ups are great, I wouldn't recommend the G5 line-up though. If you are trying to save a bit of money, the EVGA G3 1000w is a really good deal.

Good Catch on the CPU - RainStryke
 
I never even gave it any thought ... OP stated its what they Bought, and I just ran with it
 
Intel i9 9900K = Sockets Supported FCLGA 1151  <---
 
 
--->  X299 = Socket 2066 
 
donbrownz --> Better Call Amazon & cancel
 
 
PM sent to OP
 

No problem, thanks for the blue ribbon Cool GTX!
 
X299 is a great chipset. Here in 6 days we are expected to see the new i9 10th generation stuff from Intel, no idea if it's going to be on Amazon that soon though. The i9 10900X is looking pretty good. However, the i7 9800X has dropped down to 299 recently and that's an awesome deal if you have a Microcenter around... Might even be worth the drive, unless you need to spend more than $260 for gas and your time, who knows you might even enjoy it.


If you stay with the i9 9900K and return the X299 Dark, then I would look towards a Z390 board, anything with that chip set will fit the i9 9900K. If you go with the Z390 Dark from EVGA, then I would recommend going with some of this RAM:
https://www.newegg.com/patriot-16gb-288-pin-ddr4-sdram/p/N82E16820225144?Description=patriot&cm_re=patriot-_-20-225-144-_-Product

I originally purchased those and found out they were not compatible with anything I had. A guy here on the forums got his to 4800MHz on his Z390 Dark.
https://forums.evga.com/Patriot-viper-steel-ddr-4400-MHz-is-cheap-17000-ish-m2964431.aspx

RainStryke
The i9 9900K does not work with the X299 motherboard. That is a 1151 socket CPU and the X299 motherboard is 2066 socket.
 
Processors that are compatible with X299
https://www.intel.com/content/www/us/en/products/processors/core/x-series.html
 
The recommended PSU's are solid, EVGA's G3, P2 and T2 line-ups are great, I wouldn't recommend the G5 line-up though. If you are trying to save a bit of money, the EVGA G3 1000w is a really good deal.

OKAY just canceled INTEL CPU and AMAZON accepted cancellation.
 
But kids say box on doorstep of house.  Might be X299 motherboard.
 
Looked at Intel CPU link you sent,  What CPU is comparable to the i9-9900K @$471 including performance ?
The http://www.cpu-world.com/Compare/172/Intel_Xeon_W_W-2125_vs_Intel_Xeon_W_W-2175.html
 
This is a SKYLARK processor socket introduced in 2017?  Are you stating a newer Inter CPU using a X299 chipset and 2066 socket?  Im not sure what the price and performance of the CPU?

This article says not likely?
https://www.game-debate.com/news/27383/introducing-intels-10th-gen-comet-lake-core-i9-10900kf-processor-through-a-timely-leak
 
I believe it to happen because the X299 is for the new chipset.  EVGA recd the x299 chipset from INTEL. Correct?
 
This article says maybe December 2019 release and have been working on this CPU since 2015.  https://www.pocket-lint.com/laptops/news/intel/146552-intel-sunny-cove-ice-lake
 
Intel also talked about Foveros, a new tech to package processors that means more complex processor dies can be stacked upon one another rather than having to be placed side-by-side. This could enable totally new device designs that are even thinner and lighter. 
 

donbrownz
This article says not likely?
https://www.game-debate.com/news/27383/introducing-intels-10th-gen-comet-lake-core-i9-10900kf-processor-through-a-timely-leak
 
I believe it to happen because the X299 is for the new chipset.  EVGA recd the x299 chipset from INTEL. Correct?
 
This article says maybe December 2019 release and have been working on this CPU since 2015.  https://www.pocket-lint.com/laptops/news/intel/146552-intel-sunny-cove-ice-lake
 
Intel also talked about Foveros, a new tech to package processors that means more complex processor dies can be stacked upon one another rather than having to be placed side-by-side. This could enable totally new device designs that are even thinner and lighter. 
 

X299 has been around for a while, Intel is releasing "new" cascade lake processors soon for it but they are just the same skylake based processors with a very small clock boost. Not to say they aren't good processors but definitely not state of the art,  and still on the old 14nm+++ process. Intel recently launched some new 10nm mobile parts with the new faster sunny cove core but that won't be on desktop until 2021. Which you mentioned in your first post not wanting to be a beta tester so X299 is a good fit. Its been around for a good while and is a stable platform. Just watch what you purchase for it as some of the processors released on X299 are not a good value (7900x) and some just plain silly, (Kaby lake X line)