No differences in memory management or core management in any of the versions of Vista, from Home Basic thru to Ultimate. They all handle quad core and the ram they have identically. The 32bit versions are all limited to 4GB ram (even if they cant really access all of it). The 64bit versions of Home Basic are limited to 8GB and the others 16GB.
I run Vista Business 64bit with 4GB ram (on a Core 2 Duo E6600) and its just flies. The 64bit drivers were easy to find and run very smoothly. 64bit XP drivers have been around for 3 or 4 years now and Vista 64bit drivers are usually available these days. Finding x64 versions of all apps is a different thing, but 32bit apps run just fine if not.
http://hubpages.com/hub/Windows_Vist...the_Difference
http://www.microsoft.com/windows/pro...ns/choose.mspx