Scenario 1: Need (AD,AC/SQL,File Server)
Get Server 2012 Essentials (AD,AC/SQL,File Server, Anything Else) (Up to 40 users with script)
Physical or Virtual

Scenario 2: Need (AD,AC/SQL,File Server) and Exchange (Current SBS)
Get Single Copy of Server 2012+Exchange 2010
VM 1: AD,AC/SQL,File Server, Anything Else
VM 2: Exchange 2010

Scenario 3: Need (AD,AC/SQL,File Server) and Terminal Server
Get Singe Copy of Server 2012
VM 1: AD,AC/SQL,File Server, Anything Else
VM 2: Remote Desktop Services Role w/RDS CALs

Scenario 4: Need (AD,AC/SQL,File Server),Exchange Server, and Terminal Server

Get Server 2012 Essentials (Up to 40 users with script) + Single Copy of Server 2012 + Exchange 2010
VM 1: Server 2012 Essentials (AD,AC/SQL,File Server)
VM 2: Exchange 2010
VM 3: Remote Desktop Services Role w/RDS CALs