Windows 8 upgrade confusion! Help!

Does the Windows 8 "upgrade" retail DVD offer a clean install option. My current Windows 7 Home Premium "upgrade" disc allowed me to do a new install on a freshly built computer. Does Windows 8 retail offer this as well?

The reason I ask -- I currently have a WHS 2011 build that I would like to migrate to a Windows 8 install to take advantage of 3TB drives and storage spaces.

If not, I have an old Windows XP key from an unused laptop. Would it be possible to purchase a digital upgrade from the Windows 8 store, then create a backup disc to install on my server?

Thanks in advance!