SBS 2008 is based on Windows 2008 and Exchange 2007. SBS 2011 is based on Windows 2008 R2 and Exchange 2010. 4G, especially if you use Exchange, is not enough. Go 8 at the very least.

Also, 2011 has the most support remaining.

Lastly, why do a clean install? Do you not have settings and user accounts that should be preserved?

JamesNT

James Summerlin
My personal site: http://www.dataintegrationsolutions.net
james@dataintegrationsolutions.net