The sun intensity of the exact scene is set to 80% with an infinity fill light set to 10%.  Rendered with IDL, intensity 0.15%, I perceive this to be a more realistic render.  The fill lighting still needs further adjustments, either a increase in intensity or changing it to a specular light only; the sun can be adjusted also, but I would not increase it's intensity above 100%

These are adjustments I considered with this particular model without reworking the textures to more suitable shaders.