Do No Harm ... well the least harm anyway

I'm also in the camp that prefers to run my main speakers full range, and just use to sub to augment the bottom octave or so.   Some male vocals can go down near 60hz, and are best reproduced by your main speakers so the fundamental notes plus their harmonics all come from the same place, where they stand a much better chance of sounding like a single coherent music wave. .  Just my 2 cents.

Well, there you have it. It seems I have about a snowball's chance in Hell of getting this idea to sound correct. I think I will let the Nefes play full range and let the subs give a helping hand under 50 Hz or so. My subs have all kinds of adjustments, so I can mess with them and not really worry about the critical integration of 2 different drivers at the 100Hz range. Thank you ALL!!

Adjusting your subs makes the most sense to me, but I do understand what you were hoping to achieve.  There's just never a free lunch, and the downside is likely to have more overall negative impact than positive, but in fairness that's an educated guess, not a fact.  

Every room and situation is different, but I find my subs sounds best 180 out of phase, low pass filter at the lowest setting, and gain set very low so that it's barely audible except on deep bass heavy passages.  YMMV, but good luck and enjoy. 

@immathewj

Yes, I run the subs to the high level inputs off a speaker output from an amp.  In my case, I reverse the polarity at the sub input, but some subs off it via a switch.