WerkWurk

try this build 
PCPartPicker Part List
CPU: Intel Core i7-13700F 2.1 GHz 16-Core Processor  (3190.00kr @ Føniks Computer) 
CPU Cooler: ARCTIC Liquid Freezer II 360 56.3 CFM Liquid CPU Cooler  (883.00kr @ Føniks Computer) 
Motherboard: MSI MAG B760 TOMAHAWK WIFI DDR4 ATX LGA1700 Motherboard  (1498.00kr @ Alternate) 
Video Card: ASRock Taichi OC Radeon RX 7900 XT 20 GB Video Card  (7299.00kr @ Proshop) 
Case: Lian Li LANCOOL 216 ATX Mid Tower Case  (664.00kr @ Proshop) 
Power Supply: Thermaltake Toughpower GF A3 - TT Premium Edition 1050 W 80+ Gold Certified Fully Modular ATX Power Supply  (1168.00kr @ Alternate) 
Total: 14702.00kr
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2023-10-03 17:46 CEST+0200

Yes. But it's the one part that could be added later.

Your PSU is good already 
PCPartPicker Part List
CPU: Intel Core i7-13700K 3.4 GHz 16-Core Processor  (3369.00kr @ Føniks Computer) 
Motherboard: MSI B760 GAMING PLUS WIFI ATX LGA1700 Motherboard  (1402.00kr @ Proshop) 
Memory: G.Skill Ripjaws S5 64 GB (2 x 32 GB) DDR5-6000 CL30 Memory  (1768.00kr @ Proshop) 
Monitor: Asus ROG Strix XG32UQ 32.0" 3840 x 2160 160 Hz Monitor  (8353.00kr @ Føniks Computer) 
Total: 14892.00kr
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2023-10-03 17:20 CEST+0200

Little point in settling on hardware until a couple of weeks before purchase. Pricing and offerings change to frequently otherwise. For example, Intel is expected to introduce new desktop CPU Oct 17.
 
The 7800X3D would only be a good choice if most system usage was gaming. Otherwise a 7900(X) or i7-13700(K)(F) would be better choices if buying today. 
 
I suspect a different motherboard would be needed. 🙂
 
If you will be gaming at 4K you'll want to get a more powerful GPU. Will likely squeeze the budget a bit.
 
If you stick with AMD Windows 10 is fine. If you decide on Intel Windows 11 would do a better job of scheduling cores.
 
 
If the PSU is much more than 5 years old, for a new build I'd be looking to replace it. I can't imagine how an o/s would significantly affect the required PSU capacity. 
 
 

Here's an example build with the CPU, motherboard, memory and PSU you requested. I don't know much about monitors, so I might not have picked the one you wanted.
 
The 7900 is more productivity oriented, since it has 12 cores. There's a review here. It does come with a cooler, but how well the Wraith Prism copes with the 7900, I can't say.
 
PCPartPicker Part List: https://dk.pcpartpicker.com/list/ycxVwg
 
CPU: AMD Ryzen 9 7900 3.6 GHz 12-Core Processor  (3351.00kr @ Proshop) 
Motherboard: MSI B650 GAMING PLUS WIFI ATX AM5 Motherboard  (1760.00kr @ Føniks Computer) 
Memory: Corsair Vengeance 64 GB (2 x 32 GB) DDR5-5600 CL40 Memory  (1520.00kr @ Proshop) 
Power Supply: MSI MPG A850G PCIE5 850 W 80+ Gold Certified Fully Modular ATX Power Supply  (1327.00kr @ Proshop) 
Monitor: Samsung Odyssey Neo G70C 43.0" 3840 x 2160 144 Hz Monitor  (6399.00kr @ Føniks Computer) 
Total: 14357.00kr

Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2023-10-03 17:02 CEST+0200
 
I'd choose EXPO memory for an AMD system, but PCP doesn't seem to say.
 
I don't think I'd replace your PSU unless you need to, but I've included one anyway.

Far too early to spec out a build for next year. Both pricing and available technology will likely change a great deal in the next six months.
 
Some general comments on the OP build:
Consider a less expensive motherboard. Something along the lines of the Asus Prime Pro series. Then Zen 2 cpu are better matched with DDR4-3600 CL 16 memory. Consider a different storage scheme. Perhaps using more of the budget. I'd suggest at least two nvme drives, o/s and working storage along with a large amount of hdd storage for media not currently being worked on.

The part selection looks good. With your budget you might be able to squeeze a 2080 super in there but the 2070 super is still a good card. Considering you’re going for the 3950x, you might also want to invest in a higher clock speed ram like 3800 or 4000 if your motherboard will support it as amd can really take advantage of fast ram. Good luck with the build!