I can't say that I would want any boxed subs playing up into the 200Hz range (crossover point to the 8" P-Audio coaxial). The drivers used in the V-2 (open baffle) with the specifically designed SA-1 amp is just right for the job though, and do not cost much either.
Also, a 200Hz crossover point means that the acoustic centers of the drivers need to be within about 1/2 of the wavelength at the crossover point and that pushes it to about 2.5 feet.
I have not tried removing the back on the 8" kit as I am trying to keep the cost really low on this one and making modifications to the drivers would bump up the price.