so i had my friend install my 2 RE SE's and my re 12.1 sounds great. Then i got my local audio shop to install my CDT HD-62's and my JL 300/2. i got my car back after they closed and when i turned my car on a loud squeek came from the speakers and didnt stop no matter how loud or low the volume. as i hit the gas and brakes it went up and down. I asked people on here and they said alt wine and to get the ground thing, but when i took my car back in today they said it was probably bad rca outputs on my HU and when they put their memphis amp on it got rid of like 90% of it because they said it must have had better filters than my 300/2. So are they right and should i use my warranty to get a new HU or are they just fkn retarded?