My Pioneer HU preamp output is only 500mV. I know most HU's are 1.something volts & there are some that are 4 volts. Is the advantage to having a high preamp output is that you won't have to turn up the gain on your amp as much and work it harder?

Also, when setting the gain for my speakers, should I set the gain after equalization or before (flat EQ)?

 

stronger the signal. The amp can put out the same output with the gain lower. Less noise.

 

You should set amp gains with all signal processors defeated. Then set xovers. Then set EQs.