Check w/ Radenight re: doing this using the 'trick'. As far as I know, in general, basically, you cannot go 32 > 64. Not a license issue but, a technical one. You can't, in effect, mix the two. 32 > 32 or 64 > 64, only. OR do freash & clean, as long as the hardware is an x64 platform, if the native OS is x86.
I have always told clients this path, 32 (upgraded) to 64, is not an option.
Drew