Thanks! How big/complex would the excel spreadsheet have to be to see the difference do you think?
I can't give you an exact figure, but it'd be a pretty good size. Something you'd only likely see come out of banks or large corporations that have been around for awhile.
Though the other advantage of going all 64-bit would be for the sake of simplicity at the OS level. Getting all the same apps using the same libraries under the same environment makes for an oh so slightly more streamlined operating system.