The three stereo amps and a monoblock would work fine for a 7.1 system with either a 990 or a 1070 (or a 970, for that matter). You would just connect the pre-amp outputs to the four amps (use one Aragon amp for the fronts, one for the side surrounds, one for the rear surrounds, and the M200 for the center) and then hook up the speakers. There's be no need for additional pre-amps.