Going to propose a solution which isn’t overkill but is one you can grow with.
You said 4 bay but I’m going to suggest something else for you to consider.
TVS-872X-i5-8G (or the 672X)
you can populate the bays as you grow.
– you can put in 4x HDD and setup RAID 6 from the start (Important??)
The i5 is good for a 4-5 audio transcodes with ease.
The i5 can handle a couple subtitle burning sessions (1-2 depending on bitrate)
Upgrade memory if you intend to use it as a “general purpose appliance”.
PMS will run ok in 8GB but if you start using the machine as an Appliance, you’ll need extra memory.
If you’re comfortable swapping parts,
Order exact spec memory and take it to 32 or even 64GB (if funding permits)
You’ll be glad you did.
Graphics card:
A simple Nvidia P2200 will do everything except AV1 (which is the up & coming codec).
I have a TVS1282-i7-64GB, 10GbE. I’m grateful I bought the wider chassis upfront.
As I needed more space, I added drives.