I would get a monoblock stable at 1 ohm; it'll be a lot less hassle than purchasing two separate amps or a two channel strong enough to crank out 400 at 2 ohms on each channel. Look into the Memphis ST1000d, JBL BP1200.1, Phoenix Tantrum 1200.1, or something by Hifonics. You should know that peak power doesn't mean much... everyone loves to rate their equipment at way more than the stuff can actually handle. Think of peak power as the point at which a subwoofer will flip out and blow up.
This cheapie would probably work well too: