I do not use IT products intended for home use in a commercial environment
I would not use a home desktop machine either. If I go with a "main machine" instead of a server it would be a business desktop or workstation.
I'd prefer real server hardware but I'm just unsure about the OS side, seems complicated. My ideal would be good server hardware but WIN7 Pro for simplicity. But that's not offered pre-installed and I'm not sure WIN7 drivers are available for the server hardware. Plus I wouldn't want to beat my own path, if the offered choices are desktop/WIN7 or server/ServerOS then I probably want to pick one or the other.
and SQL server 2008R2 standard.
So what does SQL Server buy you over the SQL Server Express which AC installs? How does the install work does it just recognize SQL Server is installed and use it? Given my admin experience I'm inclined to stick with SQL Server Express unless there's a huge advantage.