If you put new aftermarket 4 ohm speakers in place of those, then the amps would output only 1/2 of their original wattage. Twice the resistance, half the power. See how that works?? But you can run them on your factory amps, you would just do better to run them on a new amp or on the deck.the front doors are 4x6" at 2 ohm and the back decks are 5 1/4 at 2 ohms
