To be safe, I'd say don't go above 23 for the volume. Since my car has a blue theme, I don't mind the blue knob illumination :-) but in addition, the eq has it's own volume knob, so you...well for me..... Can blast the highs with a touch if the knob. I've got my subs powered off the h/u pre outs and the fronts and rears run off the eq. Works like a charm.