Try buying prebuilts. Graphic card prices are insane right now.
Example:
https://www.dell.com/en-us/shop/gaming-and-games/alienware-aurora-r12-gaming-desktop/spd/alienware-aurora-r12-desktop
Or look for something like these
- Intel Core i9-10900K (using Intel Quick Sync Video for streaming) (CPU)
- Arctic Cooling Liquid Freezer II 360 or EK AIO 360 D-RGB (Cooler)
- Asus Prime Z590-A (Motherboard)
- 16GB DDR4-3600 C16 X2 (RAM)
- RX 6700 XT (MSRP $480) or RTX 3070 (Graphic card - MSRP $499) - For 2560 x 1440.
- Corsair MP510 960GB or PNY CS3030 1TB (SSD)
- Seagate 2TB (Hard disk)
- Seasonic Focus GX 850W or NZXT C850 (Power supply)
- Phanteks Eclipse P500A (Casing)
https://pcpartpicker.com/list/D4nbQD
If you can’t find Core i9-10900K. Core i7-11700K is another option but it comes with less 2 CPU cores.
RTX 3060 Ti (MSRP $339) will get the job done for 1920 x 1080. You will need RTX 3080 (MSRP $699) or RX 6800 XT (MSRP $649) for 3840 x 2160. RTX 3080 handles 4k better. Also, Nvidia Nvenc smokes AMD codec for streaming just in case something goes wrong with Intel Quick Sync due to application issues. Quality is terrible on Radeon when it comes to streaming.