Do you want one set of speakers that handle 400w RMS? If so, those will be hard to come by. How much power does your amplifier put out per channel? If all 4 channels added together equals 400w @ 4 ohms, I'd say look into the Focal PC 690 or the RE FR series 6x9s. Hertz speakers also seem like they will be a good choice if you want them. There are many options for you to explore.