ok i just bought a 12 inch kicker cvr 800 peak power 400 rms that is wired to 4 ohms. i have a lightning audio amp that says 250 watt at 4 ohms so the sub is under powered. would it hurt the sub at all to turn the gain on the amp to max??

 

You can turn it up you wont hurt anything, its just a potentiometer (volume ****) so set it at a desired point and you will be good.

This might be a good read by the way.
Amplifier gain controls - setting your gain

 

i actually just read that right after i post this... lol helped alot!