Servo and "power" have no correlation. As Bruce elaborated, Servo is an advanced system that is able to measure both the woofer acceleration and woofer position in realtime. This information is than feedback into the amplifier that controls the woofer movement and instantaneously compensates. Servo enables considerably more accurate transient accuracy, lower distortion, and compensates for the aging of the woofer suspension system (compliance changes).
I often like to make the comparison between a laser guided missile reaching its target compared to an RPG. The laser guided missile uses realtime information to continuously compensate for its flight path, where as once you fire an RPG, you just hope you aimed properly, or a giant gust of wind doesn't change the trajectory...
In addition, higher amplifier power does not mean more output - it is really just a marketing ploy. For example, which would have more overall output, a subwoofer with a 1000 watt amplifier powering a woofer with 84dB sensitivity, or a subwoofer with a 300 watt amplifier powering a woofer with 92dB sensitivity?
The answer might surprise you -- the 300 watt subwoofer will have TWICE the power output...
Without knowing the sensitivity of the woofer being used in the subwoofer, amplifier power is a meaningless specification.
Because of Direct Servo, Rythmik subs are able to use lower mass, higher efficiency woofers compared to their competitors.
I recommend avoiding falling into that crowd the relies on "power" as some type of measure of performance. You would be exactly who they are targeting with that rather meaningless spec