@jaytor: Give Danny Richie a call. He’s been involved in some serious investigations into high transparency DSP projects and products. He found the sound of the digital crossover in the Linkwitz LX521 loudspeaker seriously lacking, but there are much better digital systems than the ones Linkwitz used.
Say, I see you now have a pair of 2-woofer H-frames on each side, replacing your precious pair of 3-woofer frames (one per side). Do you have a Rythmik plate amp for each 2-woofer H-frame, for a total of 4 plate amps?
I made the 2-woofer version of the OB Subs, and bought the 8 ohm version of the woofers from Danny, rather than the 16 ohm. That allows the plate amp to feed the woofers their maximum possible output. Being solid state, the amp producers more power into 4 ohms than into 8, of course. And two of the 8 ohm woofers present an approximately 4 ohm load to the amp, while a pair of the 16 ohm an 8 ohm load.