Not really ... different design goals. (Good logic, though....). Please allow me to elaborate:

The built in DSP/AMP combo with the EP-600, for lack of better terms, "knows" what the driver is doing at all times. It keeps the driver under control, and also delivers a flat response, even under conditions that cause subwoofers without this type of control to lose audible performance.

The STF-3 and VTF-3 use conventional amps, as does SVS. This is not a knock on either, by the way, for the money, they are both excellent.

It is this "intelligent" amp/dsp set up COMBINED with good physics which works so well for the EP-600.