Nick,
The maximum voices test wasn't using much RAM as the VI instances were sharing RAM. However I can generally run both VI and VE up to around 3.25 GB (6.5GB total) without problems.
I have a current session that has the following set up:
Strings 9 VIs average programmes 8 per instance
Woodwind 8 VI's average programmes 7 per instance
Solos, etc 10 VIs average 4 per instance
Choir 2 VIs average 4 per instance
Percussion 1 VE loaded with 8 VIs average programmes 3 per instance
Tuned Percussion 1 VE with 8 VIs average programmes 3 per instance
Brass 1 VE with 9 VIs average programmes 7 per instance
(So total VIs 52)
Logic EXS 24 14 instances
Logic synths etc 8 instances
Omnisphere 3 instances
Play 1x12 channel instance, 1x6 Channel instance
.
12 channels of Space Designer and about 20 channels using linear eq and 8 channels of Metric Halo channel strip.
then a few compressors etc.
And an H264 video running in sync
So a pretty heavy load - there are occassional CPU overloads but it will real time bounce the whole 6 minute song without glitches.
The Play plug-in running storm drum 2 appears to be the biggest hog followed by Omnisphere. The VSL stuff runs really well and reliably.
I think hardware elements helping on my system are processor speed (3.2-8 core) 32 GB of RAM, and upgraded Graphics Card (8800GT) the dedicated sample dirves and having a fast raided boot drive. The VSL load is spread across all 8 cores very well.
Julian