This image was an experiment with various Topaz filters:

Topaz Clarity intelligent localized contrast enhancement without halos (if used sensibly) The trick is to avoid blowing out whites or blocking in shadows when contrast increases
Topaz Detail enhances detail while avoiding white halo lines.
Topaz DeNoise noise removal. It removes noise while retaining detail and used with restraint minimizes loss of micro tonality.
Topaz B&W effects has a multitude of categorized presets that allow fine tuning of monochromatic images.