Image size of the original texture map might have something to do with how sharp the letters are.

As far as the lackluster aspect: are you using a version of Poser not Pro? If so, my take on it is because of this (explained best by CobaltDream):
We want a linear workflow using Gamma Correction.  Why use a linear workflow?  The colors you see on your screen are in non-linear sRGB color space.  The calculations a renderer makes are linear and produce linear results.  If you don't anti-correct colors before they reach calculations like how to shade and highlight a surface, then they make the wrong calculations.  If you don't correct the final result, then the render will be in linear color space and won't appear properly on your screen.  That means we want to anti-correct all our color inputs and correct all of our outputs.

What this means is going into the material room and creating some nodes for each material that uses colour or a colourMap. Look up Gamma correction on this forum to see how that is done.

Bantha has a Wacro that you can run against your materials to gamma-correct them.

If you are running Poser Pro, then activate Gamma-Correction.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks