line driver voltage higher than amp

you will be fine your eq at best will give you 4volts

if it's an external eq, you can try turning down the gain to a low setting to decrease the voltage, then set the amps accordingly.

As mentioned before, if there is a gain knob on the EQ, adjust it so that it does not exceed 5V at it's max level. If there is no gain knob, and you were to theoretically 8V to your amps inputs, you may clip the input resulting in some crappy sound. Odds are though some combination of volume/gain settings in the EQ or headunit should allow you to not send that maximum 8V from the EQ and you should be fine.