After having tried many settings, in my system, the ones that work best are the following:
Steepness: 32 / Filter max lengh: 2,000,000 / Cutoff freq.: 1,00 / Anti-aliasing: 200.0 / Pre-ringing: 1.00
With these settings the sound of my system is very natural, clear and lively especially with classical music and acoustic jazz.
Mac Mini / Wireworld Starlight 7 USB 2.0 / Gold Note Dac 7 + Gold Note external PSU 7 AC / Klimo Merlino Gold / Kilmo Kent Gold / Dynaudio Contour S 3.4