The short answer is “it depends”.
Longer answer. The amount of load the CMS generates is related to how often you have the Players poll for updates, how large those updates are, what caching mechanism you implement, how frequently your content changes and how many content items are assigned to each Player. Also a factor is what logging level you run at, and whether you have proof of play statistics enabled.
You need to do some real-world measurements with typical work load with say 10 players, and extrapolate from that.
Typically though, at 2K Players, I’d be looking at a MySQL multi-master cluster to host the database (3 machines), some form of shared storage (for your CMS library to live on), three application servers running webserver/PHP/memcache - all pulling library content from the shared storage, and a load balancer sat infront of that to balance SQL, web requests and XMR.
If you opted for very long polling intervals though, you could massively reduce that requirement.