That would explain a lot, however Autodesk states on the Softimage website
Even faster performance is possible with the optional addition of an NVIDIA® CUDA enabled GPU.
and the Quadro's are most definitively CUDA enabled
The Quadro drivers however sport the option to turn PhysX on, so that seems to slightly contradict the remark you found on the NVidia forums.
This seems to be the more or less official stance at Softimage:
You need an NVidia card that supports CUDA, and you need to enable PhysX hardware acceleration in the NVidia control panel.
quoted from here
And when I logged a Support Request so long ago, I expressly stated I was using a Quadro FX 3700, even accepting it could be a hardware limitation (they just failed to mention) so I assumed that the fact that they didn't simply reply that it wasn't PhysX enabled, but "merely" CUDA enabled wasn't the main problem.
But I've given up on this feature altogether. Everybody (including me) is always raving about the quality of Softimage Support, but in this case I feel "slightly" let down by them...
PS As a moderator on this forum, I must point out the necessity to use the so called URL-Tags surrounding any kind of link, as the links won't function as links, but are merely plain text, if you don't place them inbetween URL-Tags...
PS2 - Welcome to our little forum...