zbrush - xsi: Creating high definition 3d models

What is the best approach in creating high definition 3d models in zbrush and xsi?
I've seen Taron doing some amazing stuff with low poly cages and displacement maps in Messiah. Will it work in XSI?
Thank you.
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Fiery

I don't see why it shouldn't work in xsi.
Here is how I do it.
I create a low poly mesh that represent the general form of the final object while smoothed.
Import this to zbrush and add all the details.
then you have 2 options one is to export the normal maps and or height maps for displacement.
The other way is to export the high rez object to xsi and use ultimapper for baking the height maps.
The next step is to apply the height map to your low resolution object.