Okay, here's the final update (I think)
Poser Pro does not properly import (into the material room) the 64 bit image concerned, so there is no chance that it will work for me. What's happening is that it cannot read the image properly and so the image hue gets pushed way bluer, and much of the gradient nuances are lost as well.
So...I'm off to try to settle the issue of which program I will go with. I'll probably stick with Lightwave for now, because I'm used to it, and there is a decent amount of Poser (assets) to Lightwave pipeline interest / tutes / training out there. In the long run, I'm not sure. Whatever can use nice cheap Poser assets the easiest.