Do i change my amp settings?

setting the gain and adjusting all those other settings is basically tuning your system. look up how to tune a system correctly or go to a car audio shop and have them set everything perfectly for you, it costs like 20-40 bucks. bass boost should always be set at 0 so it reduces your chances of blowing your subs. if you want to do it yourself, you can do it by ear by playing a constant 40hz bass tone and adjusting your gain like that or use an oscilloscope by reading the waves.

If you change a sub, you should re do your tuning. Although there are only minor differences in the subs, you can not know for certain if the specs they say are on the sub is what it is actually handling. I personally cant tell you what to set your gain to because i dont know what it sounds like...

Keeping them the same, is a good way to start. You might want to tweak it a little, so play a little. I would keep the gain matching your output voltage on your deck, as that's how it's supposed to be set always, but what your changing to matters, like from going from sealed to ported enclosures matters, as does woofer size..

Good Luck!