Thanks so much for all the great advice!
I forgot to mention that I am driving them with a McIntosh MA8950.
They are plus or minus 3 db at 31 hz. Ask Wilson what order the speaker is
2 nd or 4 th and stick with that Go around 37-38 hz. You never want overlap
at least 6 db higher for your specs are not flat at 31 hz try 73 hz kthey 38
on. A bunch of music , btw the Martin logan subs are not in the same league
a Svs 4000, or ultra 16 much better controlled ,the JL audio Fathom are the best of the bunch ,sealed are always more accurate then vented or passive radiator .
the ML subs are decent ,I am just speaking in absolute terms.
Unfortunately, my budget is exhausted after the McIntosh and Sabrina's so the subs are a carryover from my prior system. The remaining $$$ is for proper cables. Frankly, the way the room acoustics are optimized when the Wilson dealer was setting the Sabrina's up they were tricked into thinking the subs were on when they weren't.
One thing I should have mentioned, is that in-room performance of speakers has almost nothing to do with the specified or quasi-anechoic (Stereophile style) measurements.
Room gain is real, as are room modes which can move the bass output singificantly up or down. Setting a sub or crossover by published specs is really tough compared to doing it by measurement.