1- Xp 64 bits is out and works fine, and Vue should be able to run more than 2 gigs of memory under this OS, otherwise there wouldn't be a point in releasing a 64bit version.

2- If you get the xtra modules for 5, you get 5ProStudio, so my guess is you'll be able to upgrade from 5PS to 6PS.

3- getting too complicated for my single braincell, sorry!