You need to do a slow break in to achieve best output of these subwoofers. They are very large and roughly 40 ~ 100 hours break in should give you that fear driven thumping experience.
The gain on an amplifier should not be confused with the rms/ overall power the amplifier can deliver. All the gain does is match the output impedance of your source ( i.e. imperdance at your deck's / preamp's RCA output) to the input impedance of your amp (RCA input of the amp). When its properly matched, you will find as you turn your volume control up, the amplifier increases the power output to the speaker proportionally....hence the "gain" is matched. You cannot make the amplifier give out more power with higher gain..all you do is make the amplifier jump faster than the volume intended. Sounds great....until you start introducing electronic noise at the amp (as it got very quickly into it's "noise" range ) and the speaker plays something it wasn't supposed to. play