Need to add a new NAS to existing SB network

[Enquiries]

We currently have a Synology DS415+ that we use exclusively as a file server. We are fast running out of drive space so it is time to add a new NAS. I am generally very happy with our old NAS and it has served us well. We have 8 workstations and 2 or 3 laptops on our network. We use an Asus AC3100 series router for DHCP and first line hardware firewall duties, but our workstations are on a static addressing scheme. One thing I would like to do is convert our old .mdb project database to a SQL database (or a compatible derivative) that would only be accessible from our intranet, if possible. Ideally, we could just extend our existing shares to create more space without having to move a bunch of data to the new NAS. We mainly store our project database (under 10 GB), documents, photographs, AutoCAD/Civil 3D dwgs, and 3D laser scans. I was looking at the Synology DS920+ with 4 10-TB drives about a year ago when I started thinking about this. Any ideas?