For a little office of 3 or 4 people I thought of installing OMV on their PC that has an AMD F2 5300 CPU (AD5300OKA23HJ).
In addition to RAID5 (4 HDD 1TB), sharing with Win10 PC and backups, I don't think there is any need for anything else.
The CPU is a dual core, but I think it is sufficient.
As memory I thought of 4GB.
What do you think?