I have 3 radio stations streaming online where I buy slots from reseller, I would like to get my own server, is there a guideline to size,

My station averages 2500 slots at 56k at peak

Thank you for your response.

If you're running AutoDJ, gets a decent CPU. Else the main thing to ensure is that you have a fat uplink, ideally 1Gbit or at least 100Mbit.