The Microsoft licensing is a bit batty now for Windows Server 2016, but the long story, short version is: per physical server, you must have a minimum of 16-cores licensed, so it makes sense to get 2 physical CPUs with 8 cores each. If the new server has more CPU cores, then you need to add more Server licenses. Once all cores are licensed, that entitles you to run 1 x Windows Server instance on the physical server, or two virtual Windows Server instances. The one allowable exception is to run Windows Server 2016 on the physical server with, and only with, the Hyper-V role (no files/servers/AD/etc), and then you are still free to run two virtual servers.