Is changing the SQL Server port really that much safer? SQL Server's default port is 1433. I've been told by our admin that the port has to change "for security reasons".

Is it really that much safer to change the port? If the server is behind a firewall and it only allows connections to it from a certain range of IP's, is that not good enough?
It helps against common port scans that can be initiated through port scanning websites. But it won't help against a committed attacker. It's just another layer, but doesn't add much over the firewall, as you mentioned.