Running the signal through the sub's crossover obviously requires that the crossover network be of good quality. I would not do this if your subs only have passive, speaker level crossovers. If the sub has line level crossovers, the best course of action is to just hook the system up for stereo subs and listen for any negative contribution from the sub's crossover. A call to the sub's manufacturer might give some insight into the quality of the crossover.

The Outlaw ICBM can also be used to do this setup, and it is of high quality.

I wouldn't worry about the length of interconnects. Just keep them away from AC power wires (a good idea no matter what the interconnect length).