I think, you requires system that works OK for Stock Market, 4K Movie, Songs and works of for up to 15 yrs.
Here below is my case (system experience), as I'm too of your thinking that build NEW system that last for 15 yrs.
- I was using Intel i5- 2nd Generation from 2011 to 2020 (12 GB DDR3 RAM, Seasonic II PSU, Intel Original Mobo DH67BL & Cooler Master Cabinet, 1TB Seagate HDD).
- Power Supply - Seasonic 400 II, failed in 2018 and replaced with Corsair 500
- Gskill DDR 3 RAM Failed in 2020 and got replacement of same
- Intel original Mobo Failed in 2020 and unable to find any good brand board so bought Generic but it starts showing some issue
- so in 2020 Bought Intel i3- 6th Gen Processor + Gigabyte Board + DDR4 RAM (all 2nd hand) and using other parts from above old system and the same system still running
so from above Example, if you want STABLE SYSTEM than go with Intel, but keep in mind that intel Motherboards are very high cost & if same get failed after 5-6 yrs., will be VERY VERY HARD to buy NEW and if you wish to go with 2nd hand board that match your Intel Processor than it may be also hard to get.
2nd Option is AMD, for your work go with AMD 5600G (with onboard iGPU) or Higher with Onboard iGPU for BluRay/4K Movies. I will suggest onboard GPU, so no headache of Graphic Card or it's failure and also you are not in Gaming so why waste money in Graphic Card and than higher consumption of Electricity and pay higher Bill.
No worry about Motherboard Failure with AMD as you may get AMD Boards easily till 8-10 yrs., that support old AMD processors, but you may require good Cooler to keep AMD Cool for 16 hrs. run.
I don't know if Graphic Card add any advantage to watch 4k Movie.
I have no user experience of AMD, what I have suggested here is just what I read here on TE from fellow member post & their uses experience.
Actual AMD system users experience may be differ than my above views.