I myself have nearly no experience with such large setups, but maybe the following thread can give you some insights:
This focuses mostly on the IDO DB performance.
Some generic thoughts:
The resource requirements depend heavily on the checks used.
Something like check_by_ssh, check_tcp or other small checks have a small footprint, other checks, e.g. check_nwc_health or similar have heavy footprints eating up memory, especially if they have a high execution time.
I guess the database and the webinterface is/will be on a separate server? This would take some load the monitoring servers.
The load you describe for your satellites are pretty low for 32 cpu cores, so you don’t seem to have a problem here.