Why 2? Why not just run one? Yes, two would produce more power than one (about 15%) but is it worth 2x the cost and current draw?
Keep in mind that since the 2 speakers can handle 1000 watts, and the amplifier produces 850 at 2 ohms, does not mean that the speakers can handle whatever you toss at them. You still have to pay attention to distortion.
Also, that power rating is probably for a sealed enclousre with 1.25 cu/ft per speaker. That number lowers when you use a ported or bandpass enclosure