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I think that this may be a blessing in disguise for lmg finnaly enough to make quality content that the team will be proud of for once (hopefully) and less let's test a 40$ mic seriously!

2017 Fabia IIRC is on same platform as Polo 6R/6C and being an owner of the said Polo, I can tell you your options are kind of limited when it comes to introducing another audio channel. 
 
Door speakers are riveted and are a relatively minor pain in the butt to remove, you can find drop in upgrades from couple of German vendors (or you could last time I checked). Subwoofer on the other hand is a major work; you can either T off FR and FL speakers into a crossover (This may not be the proper term, I am very tired) adapter then into an AMP then to sub. Another issue is Polo chassis of that era lacks proper 12v source in trunk, so that means running thick gauge wires from  battery through the firewall all the way to trunk (it can be done but it’s just whole lot of sweating). There is also the aftermarket or retrofitting higher trim radios that support subwoofer. There was a dynaudio addon subwoofer for some VWs that you can retrofit but I don’t remember what exactly it took, but it wasn’t cheap.
 
IIIRC, You can retrofit MK6/MK7 audio stuff too. If you can find them for cheap they are not bad.
 
 
THAT BEING SAID, (4 door speakers, 2 tweeters up front) speakers in my Polo are really good considering I have the poverty spec model. Maybe you need to tweak the settings?

i mean.. it's a skoda.. probably just putting in "actually acceptable quality" speakers in place of what garbage they have in there will probably make notable difference.

Your parts list looks perfect
AMD recommend a 750W PSU for the 7900XTX so something like this would be plenty (unless you plan to do a lot of overclocking - if so there isn't really a way around paying $300 for an 1000w sfx)
https://www.amazon.com/Cooler-Master-Efficiency-Included-Warranty/dp/B08LP6WS35/ref=sr_1_3?crid=6K1DM0NL8HJG&keywords=850w+sfx+psu&qid=1682267431&sprefix=85w+sfx+psu%2Caps%2C354&sr=8-3
 
you might also want more storage than that if you are planning on playing lots of games - go with a 2tb nvme
 

Your 1650 super will sell for $100-130 (or closer to $200 if it is actually new). A new PSU is going to be ideal, your current one can sell for around $30, so your budget could be extended to £950 ish. Your storage looks good.
For that budget, I would recommend this:
https://pcpartpicker.com/list/K9Hswc
(the CPU cooler is not necessary but will make your PC a lot quieter.
 
edit: is the budget of $800 including peripherals?

Thanks for everyone's help! Despite the 6700xt having slightly better performance, I went for a 3060ti - won a founders edition for £300. This is about £20-30 cheaper than any 6700xt's were going for, and I will make use of DLSS (which appears to be much better than FSR in terms of quality) and some ray-tracing so this makes sense for me.
I will also order a 5600 to go with it.

Thanks for everyone's help! Despite the 6700xt having slightly better performance, I went for a 3060ti - won a founders edition for £300. This is about £20-30 cheaper than any 6700xt's were going for, and I will make use of DLSS (which appears to be much better than FSR in terms of quality) and some ray-tracing so this makes sense for me.
I will also order a 5600 to go with it.

If you are Ok with needing to upgrade motherboard, and RAM when you upgrade in the future, then this will save you some money now. https://dk.pcpartpicker.com/list/MH47tn
If you want to build a more 'futureproof' rig, then I would recommend this: https://dk.pcpartpicker.com/list/T4NMzf

Used 6700xt's seem to go for just over £300 - I reckon that would be worth it

Look at a used 6700xt or if you can find one cheap a used 6800
 
Cpu wise look at a 5500 or 5600 (prefer 5500 if price diff is >20$), you can problably resell your current cpu for 40-50$

AMD's cards have FSR, which does the same thing as DLSS.

If you are worried about PCIe version, go for the 5600 as the 5500 only supports PCIe 3.0.

6700xt for 360 would be my go to.  
 

I second this. I would check out some lower end 3070 cards. A little risky, but may be worth it

Having worked with these type of LEDs on the ESP32 myself, i have to agree with everything @artuc is saying.

The ESP32 runs on 3.3v logic but has the ability to take 5v input via the VIN pin.
 
Fair warning though: using the VIN port while programming your ESP via USB can cause fatal damage to your computer (ask me how i know -_-). I recommend you flash the board with EVERYTHING disconnected except the USB port. Once flashed, reconnect your components and reboot.  I'm sure there's a proper way to do it but this works too.

Now for the wiring.
The last time I worked with LEDs, I connected the VIN and the LED 5V in parallel with my PSU. PSU ground is in parallel with ESP GRND and LED GRND.
For the data pin, I am not too sure if it would will work directly with the ESP32s 3.3v logic although, I dont see why it shouldn't. Give it a shot; if not, use a shifter to boost the voltage.
 
On the code side of things, if you're using the Arduino framework on your ESP, the code here https://randomnerdtutorials.com/guide-for-ws2812b-addressable-rgb-led-strip-with-arduino/ should work without any issues.

Have you got the pinout for your ESP32 ?
 
Are you on the 5V pin or VIN on your ESP. Should be on 5V.
 
Also keep in mind how much you're trying to draw here for anything other than a very small strip.
 
Anything more should be an external power supply (or say a usb c setup of some kind)
 
From some very quick googling ESP32 are 3.3V logic level and I believe your strip is 5V, so could be problems there and may need a shifter.
 
Also could be an underlying issue like something outright faulty.

As an important side note, these LEDs are ESD sensitive as hell. I went through a couple of reels of these WorldSemi LEDs at a previous job, and we noticed they're surprisingly ESD sensitive for a modern device. So do take some ESD precautions while working with that LED strip, or you might kill it outright.

Judging by the frequency response of your mains,
 

 
Set the LPF to 80Hz.
 
Set the phase by listening to some music and fiddling with it. What ever settings sounds best, keep it to that.
 
If you have the methods to measure your systems FR available, then use whatever setting measures best.

If you have only 1 sub, you don't need to touch it. It's for adjusting the phase of multiple subs so they work best with each other.
Usually ~80Hz is a good place to start. You can use the R1700BTs frequency response to inform your choice. If you can configure a crossover with whatever you are using to drive the speakers, that would be best. Otherwise, whatever sounds best to you. 

As above, 80Hz is common.  Without getting a meter actually measuring SPL.

Zen+ is still supported by the latest BIOS version otherwise MSI should've mentioned in the descriptiont he the support was voided. https://www.msi.com/Motherboard/B450-TOMAHAWK-MAX/support#bios

Yes all AMD BIOS still support the 2000s chips

Sure weather his board can support Zen 3 is only half the question. Even if he can, I have doubt a 320 board won't cook itself alive and throttle a more powerful 5000 series CPU the second it's turned on.

Yeah, you should be able to flash the bios, but you couldn't boot anymore after the bios is updated, so update bios, let it reboot, then wait a bit, shut the PC down and swap the CPU.

All am4 cpus can fit the a320 board, its more of a question of thermal throttling the mobo. Using the stock cooler might help a little bit since the fan is blowing upwards, but you'd probably have to look at reviews of what that specific board can handle.  Imo the priority should be 
1. Cpu upgrade, with perhaps a needed mobo upgrade as well. 
2. Dual channel memory
3. Anything besides a hdd
4. Dgpu, with this budget at least