One thing to note.

@@Datefirst is affected by things like the defaultlanguage property of your language.

I believe that for the US @@Datefirst defaults to 7, whereas if you set up your login to use British English, as we brits often do, it will be 1.

This will affect what Datepart(weekday, getdate()) returns.

Just something to be aware of, I've had problems with this before.