I would, probably controversially, use Windows Server 2012 on mid-range HP DL or ML series kit. Since Windows 2008 R2 and the scriptability provided with PowerShell and PowerShell DSC have come around, it's a better compromise on usability versus automation that anything else I've seen so far. Not only that, it has a huge supported lifecycle.
Bear in mind I come from a very strong UNIX background going right back to M68K Sun3 era, through Solaris/HPUX and Linux and have used all on the desktop.
I would, probably controversially, use Windows Server 2012 on mid-range HP DL or ML series kit. Since Windows 2008 R2 and the scriptability provided with PowerShell and PowerShell DSC have come around, it's a better compromise on usability versus automation that anything else I've seen so far. Not only that, it has a huge supported lifecycle.
Bear in mind I come from a very strong UNIX background going right back to M68K Sun3 era, through Solaris/HPUX and Linux and have used all on the desktop.