noise in speakers

hi hopefully someone can help me . I just recently bought another amp for my car and had my uncle install it. now he told me that i might get the noise in the speakers because of bad grounding and that he had a thing to get rid of the noise what exactly do i need to do or get? I have 2 phoenix gold octane r amps. one is a one channel 1,000 watt sub for my 12" KICKER L7 and the other is a 4ch 125 rms per channel that i have hooked up to my infinit kappa 5X7's and 6x9's. the four channel amp has a config switch the only way u can configure it is hp/hp and lp/lp. i want my fronts to have highs and rears to have lows there is also another config which is by/lp and when i leave it on this setting that is when i get the gas pedal buzz. when i put on hp/hp its too much highs out of thr front and rear and the lp/lp out of the front and rear. my question what would be the best way to configure it for sound quality? would i need an eq. also as far as the amp config goes. he wired the rca cables from the deck to the 4 channel amp on the same side of the car and the battery wire from the 4 channel amp he had connected into the battery connector on the sub amp same with the ground wire. I kinda didnt want him to install it but he did it for free so i was like what the hell but i really need to get rid of the noise cuz it is really annoying when the volume is low u hear it more than ever.

Also i forgot too mention that the wires on the 4 channel amp are only 10 gauge whereas the wires on my sub amp are 8 gauge can this play a big role?