A good class D amp, i used to have was the MTX 500D. You could go with an MTX 6500D. It's rated at 500watts into 2 ohms, but so far all the MTX amps i had exceeded the power rating by at least 150watts. The birth certificate on one of my subs were 625watt rms into 2 ohms, and the other was 613watts rms into 2 ohms. Distortion is also underrated. Much lower than what it was supposed to be. the price of these amps are about 350-400, depending where you look.
