For Lanzar...Yea. Probably distorted as heck. To adjust the gain, Match it to the pre out volts. I turn the gain down, turn up the HU till it starts to distort, turn down a notch, then turn up gain till it distorts or clips, turn it down a hair and you done. Just do not exceed the set points of the volume level you set. If you set it for like 60/100 then anything past 60 is gonna sound like poo poo. If you want it louder then that, buy a new amp.
I'd say that's way high. Amp sensitivities vary, but generally they run from about 1/2v to 4v or so. Unless your HU has unsually low voltage pre-amp outputs it should be somewhere near 50%, or less if you have high voltage pre-outs.
The idea is to have the amp producing the most power with your HU volume at or near its max (max w/o clipping).