Streaming, audio, (more) "futureproof"... Ryzen 3900X 12-core better.
My basket at Overclockers UK:
Build fee about £100 - inquire in Customer Service Pre-Sales forum for a quote. When OcUK builds a system for you, it comes with three year warranty.
And then I see the Acer X34P in stock for £700 elsewhere. OcUK also lists it at £700 (out of stock) if you want to ask when it's available again. Usually for fast-paced fps games people use either 2560x1440 (semi-competitive, more real estate + visual enjoyment) or 1920x1080 (very competitive). But there's nothing stopping you from Ultrawide 3440x1440 if you prefer. Just could save £300 there and get a 2560x1440 165Hz screen.
CPU cooler is extremely quiet.
2080 Super more value for money than 2080Ti, is a good choice for 3440x1440 120Hz, especially with new Nvidia cards this year (latest estimate September). The Zotacs have the best warranties - 5 years if you register. You could also go with a 2070 Super for now, £200 cheaper.
The prices for 1TB and 2TB NVMEs are ridiculous just now, so specced a 500GB NVME + 2TB SATA SSD combo. Windows and programs on NVME, games and files etc on SATA SSD. Since you do audio work, if you can avoid noisy mechanical disks all the better. But you can always add some later on if need be.
You don't need an X570 motherboard for futureproofing other than for PCIe 4.0 (which will be old news in a couple years anyway with PCIe 5.0 or 6.0). You could always get a B450 Pro Carbon for £80 less. You could also get a cheaper 8-core Ryzen 3700X which would probably be fine for all your needs, and if you ever needed something more beefy then slap in a Ryzen 4000 series 12-core when they come out later this year. However, if you don't like tinkering in your case, then best to just get the 3900X now.
You don't need to spend £130 on a case either, it's just a good case and made up the rest of the budget. Most of the front panel is detachable for airflow, or can remain on for more silence.
Is there any other stuff you need included in the 3K budget, like keyboard+mouse, headset?
Wifi needed?
Cheaper spec to compare:
My basket at Overclockers UK:
+ Build fee - about £100
+ Pixio PX7P 27" 2560x1440 165HZ IPS monitor - £400