Just a quick note - I've been running SBS 2008 for 2 years and I really didn't think about running AC on the server. An SBS server is busy - it's running Active Domain, Exchange Server, DHCP servers, antivirus programs, providing several shared public resources, possibly a fax server, outlook web version, internal business website - etc. Microsoft really doesn't want you to put your line of business software on the server - that's why they provide the premium edition. You don't need the Premium edition, but you should consider having a Windows 7 Pro machine to run the AC SQL database.
