What specs are needed for a deployment server to manage 1500 - 2000 forwarders in a multisite indexer clustering environment?

Hello, I am assembling a multisite clustered Splunk implementation. I am having a little trouble finding what sufficient specs are needed for a deployment server that will manage between 1500 - 2000 clients between 3 sites. Please advise on the CPU, memory, and storage. Thank you, Tom Forbes