Bass settings are the single most requested adjustment, and the right amount depends entirely on how much low end you want.
For subtle warmth, try +2 to +3dB at 60Hz. For a noticeable boost, +4 to +6dB. For heavy, bass-forward playback, +6 to +8dB — but watch for boominess or distortion at the higher end of that range, and pull back if the low end starts to feel loose.
The higher you push the 60Hz band, the more likely you are to hit clipping on already-loud tracks. Keep the Limiter switch on whenever using the stronger end of these bass settings so peaks are caught automatically.