Why limit yourself to plate amplifiers? A stand alone ampllfier is more flexible, as well, you are less likely to have potential noise/hum issues by sending a high level signal(amplified) to the subwoofers at distant locations as compared to an unbalanced line level signal.
Also, if you go with a stand alone as an option, you can choose a Behringer EP2500. You will not likely beat the quality/price of a Behringer EP2500, or even come close to matching this quality/price combo from another company. Full band, extreme high power, very high quality build, very low distortion, very low noise and very low price.
-Chris