Brian, let me get back to your initial question. This is how a setup on Mac with lots of RAM and the use of Sibelius and Vienna Ensemble without Logic would work.
Due to limitations in a 32-bit system, it is not possible for a single application to load more than 3 GB RAM. It is indeed possible to load additional stand-alone instances of Vienna Ensemble, which will allow you to load the same amount of sample data again. If you want to open more than one instance of VE stand alone, you have to copy the Vienna Ensemble application and name it differently. The stand alone instances are not recognised from within Sibelius. You have to open them from the applications folder.
In order to communicate from Sibelius with stand-alone VE you have to use IAC or a different MIDI Loop back. Be aware that you cannot load the sound set if you choose IAC or a hardware MIDI-out. However, there is also a way to solve this problem. Open the sound set with the sound set editor or a text editor and change the entry PatchLoadMechanism from "Fixed" to "MIDI". Save the sound set with a different name. Now you can communicate from Sibelius over the IAC-Port with the Stand-alone Vienna Ensemble and the modified sound set takes care of the articulation changes.
The Sibelius and Vienna Ensemble setup guide is also available at this location: http://vsl.co.at/en/68/498/943/239.htm
Best wishes,
Andi
Vienna Symphonic Library