Actually, you need 3 licenses.
1 * Backup Exec
1 * SQL Agent
1 * Exchange Agent
The SQL and Exchange agents include a Remote Agent licence, so you don't need a separate one.
With the above agents, if you add an additional server, you don't need an additional license for the new server (provided you are backing up files only).
I don't know off the top of my head about the SBS version backing up remote SQL.
To be honest, from a business point of view, I'd stay away from the SBS version, as it then ties you in to SBS, and if you upgrade servers to non-SBS version, you'd have to repurchase BE.