Thanks, guys. This unit has the standard 100Hz crossover frequency. Originally I thought this was the best place for it, given the slope diagrams on Marchand's website. It occurs to me, though, that asking my down-firing sub to reproduce frequenies over 100Hz - against the maker (ACI) recommendations - is foolish. I plan to order an 85Hz module today and see how that goes.
Right now I have the sub's crossover set 10Hz higher than the crossover, but I'm not sure that's where it should be. Is there a standard relationship I should be looking for between the electronic crossover frequency and the sub's crossover frequency? Big, I don't think my ACI Titan will allow me to truly bypass its LP filter altogether, but I'll check. That would certainly be best.
Stephenson, I'm delaying room treatments because I'm moving in 3-4 months. I'll certainly look at treatments in the new place, though.
Eldartford, I always enjoy your posts. Thanks for helping me out. I look forward to whatever other thoughts you guys have on this!!