Personally I would run those full range and just dial the sub in with a low crossover. Or use a DSP based low pass for the sub or something like the JL Audio crossover just for low pass, Those are big speakers you'll be missing a lot of what they can deliver at low frequencies and the sub can be located by ear because it is playing above 60- 80 Hz.
Reference 3A 's special sauce is that they don't really use a crossover themselves , they use a filter cap to protect the tweeter and those woofers are essentially run full range. I believe all of their speakers are like that.
I like subs, but they can do more harm than good if you operate them crossed over that high.