Rep Power: 347

I have a subwoofer preout adjustment on my head unit. Is it better to leave it at the default setting at the mid point, or to turn it all the way up...or turn it up to 75%? I of coarse would lower the gain on my x-over and amp if I turned it up on the HU.

 
Rep Power: 0

I would keep it at 0% and set the gains properly on your amp. It will sound cleaner that way. If you want to get louder you can always crank it up more but it will not sound as good.