Amp crossovers or Headunit Crossovers
 

Which set of crossovers should I be using. As of now, I have the Amp set to high pass with the headunit set at a HPF of 100. Should I turn one of them off?

use the headunit if you can turn the amp ones off, then you can play around with the settings from the drivers seat.

On the amp there is a flat, low pass, and high pass setting. I'm assuming the "flat" setting is the same as off?

Also, even with my HPF only set at 100 on my headunit, the mid bass is extremely impressive. It sounds very tight and gets plenty of loud. If I lower the HPF on the headunit any more, its sounds even better, but I'm afraid it may damage the mids. Will too much mid bass cause damage?

if it still sounds good and they aren't bottoming out or distorting they are fine.

What kind of deck????

Pioneer 4800

I have mine playing from 60 hz @ 18dB/oct when in SQ mode. If I'm cranking it, I'll usually change the setting to 100hz to protect the mids.