Nims

Hi fella. I currently have a headunit running 2 front speakers and 2 rear 6x9". I have a 400watt boss amp running my 10" sub. Now my 6x9" speakers sound shithouse....distort to early......what should i do? Im a n00b. *new 6x9's? *run another amp for rear speakers? If i run another amp how i do it...i aleady running an amp for sub cheers!