No problem... think of the line leveler as a filter/resistor...
The unaltered signal from the head unit (factory configuration) has a specific EQ file that adjusts the signal via the DSP ( Digital Signal Processor) throughout the volume range. In simple terms...As you increase volume the bass is cut down and treble is increased, which makes you believe you have good sound at highway speeds with the wind in your face. This configuration is already amplified and should not be amplified again externally with another amp.
Line Levelers flatten the EQ curve throughout the volume range to get a level signal to the external amp... the flash just flattens the EQ curve from the head unit giving you a cleaner signal.