@Philip,
OK, take this in the spirit it was intended.
First, we need to define server both in software and hardware. Technically, the definition of a server is a computer that all other computers connect to share files or a database, etc.
I think of a server as being server hardware such as a Dell T410, etc. and a Server OS. Therefore, for me, WIN 7 Pro on a workstation computer is not a server but more a "main computer"
So, I would use that term, "main computer" for your question.
Now, will a server (server hardware and software -- OS -- Server 2008, etc.) make v6 faster? Absolutely. Will it be extremely noticeable? Probably not. But, in my opinion, and many will argue, overall you are better with a client/server setup (meaning a real server and OS). Can you put 2008 on a workstation. Yes, if it can handle 64-bit.
Another thought is and WIN 7 OS can handle 20 concurrent inbound connections. Server OSs are only limited to their CALs. Well SBS is limited to 75.
Now, the interesting comment you made is "Do I need SBS compared with Server 2008?" The way I took that to mean is that you consider SBS to be needed for a larger network. It is just the opposite. Server 2008 is generally used in large networks such as hospitals and Google, etc. You certainly don't need Server 2008 in a small business. Server 2008 can have multiple domains and subdomains and have multiple servers on a domain. SBS can only handle 75 computers and can only be the one domain controller.
What you want if you go with a server OS is SBS 2011 or 2008. Microsoft was in an awfully good mood when they came up with SBS. It is called Small Business Server for a reason. And, it comes with Exchange and SharePoint. SharePoint is the least used, best application for a company ever designed.
SBS is also much easier to set up with the wizards and easier to maintain. It is less expensive. There is no decision between the two.
Also, with a 64-bit server OS, you can run almost unlimited RAM. Most workstations can't support 12, 20, 24 GBs of RAM such as the Dell T410 or T620.
