Just for the hell of it, I decided to run wires from the diffuse and specular value channels, as pictured, to the texture, and have found the reults encouraging. The new texture settings render with a lot more detail but they are also very contrast-y. Any thoughts or suggestions?

For one thing, as far as I know, connecting the texture into Specular_Color whilst set to 'absolute' black (i.e.: 0/0/0) will have no effect whatsoever. Absolute black in the specular color channel is equivalent to 'OFF'. The contrast may be a result of using a color map as a bump map. Certainly looks that way in the material surface view.

I'll give it a whirl and hope it works. Thanks.

As mentioned above, the connections to Specular_Color and Specular_Value are doing nothing. The contrast is due to plugging the texture into the Diffuse_Value channel. What this tells Poser to do is "Make light things on the map lighter and make dark things on the map darker". There are much better ways than this to bring more contrast to your map and provide more control - such as using a bit of Gain between the map and the Diffuse_Color channel. The extra "detail" you are noticing is due to the bump map - adding a bump map to most textures will increase the detail and make the skin look more realistic.

Gain? Where's that?

Trouble is, just using the normal texture as a bump map can do odd things. It's the greyscale value that decides how high a bump is -- now imagine what will happen if you use a texture map for a character who didn't take off their swinsuit to get an all-over tan.

Here's a little trick for the bump... I found it in a thread recently, I'd love to give credit, but I don't remember who or where it came from. ...create a math node at your bump, use subtract, and subtract your texture from 1.

This is what I mean. I also use displacemt.