Brian,
the Vienna Suite uses 64-bit processing internally on both Windows and Mac, even in a 32-bit architecture.
Under Windows - each plugin comes as native x86 and x64 varieties. On Mac, we only offer x86/ppc versions - since there are no 64-bit capable hosts yet. As soon as hosts become available, we will release the Mac/64bit version for Intel CPU's. We will most likely not support ppc64. (And I strongly doubt any 64-bit Mac host will support ppc64 as well)