Trying to give something back to the Community...
The following post from the Configuration Manager in Microsoft IT blog details the hardware specs for the various ConfigMgr Site Roles used internally by Microsoft IT and it makes for very interesting reading:
http://blogs.msdn.com/b/shitanshu/archive/2010/10/22/configmgr-site-role-hardware-used-in-microsoft-it.aspx
Read the complete post at http://wmug.co.uk/blogs/cliffs_blog/archive/2010/10/25/configmgr-2007-site-role-hardware-used-in-microsoft-it.aspx