Advice needed for media server, medium sized video production company

Howdy, i’m looking into building a server for my work. I’ve just started at the company and they have tasked me with getting a new media server.
It has to have NAS but am otherwise open to suggestions, budget is an issue but I think they will spend on the right solution.
We have about 4 full time editors, all mac based currently but in future will migrate to PC.
They are looking for around 40/80 TB storage with a seperate back up drive at different location.
Any suggestions very welcome?

As you mentioned it is for a small company I mentioned reliability is really imported.
Therefor I would not recommend building anything by yourself.

I would go for a bigger Synology nas like this one:`

Your company should see this as an investment.
Synology gives you lots of uses other then just storage.
Like a VPN, Offside backup etc.

Also the interface makes it really easy to use.