Just getting back to everyone because I have my six pack and it set up properly buy a local St Louis dealer. It is pretty amazing. Two things I learned help answer my questions that I originally posted:
1. Regarding the potential overlap of subwoofer output with the low frequencies of the main speakers, The dealer reminded me that in room response of the main speakers is not nearly what it is in an anechoic chamber. So there are bigger gaps in the low frequency then we might imagine. He did confirm that the goal is to make the subwoofers made perfectly with the main speakers and not create overlap.
2. Regarding how subwoofers that are producing primarily low frequencies (although crossover of the subs does allow them to have some output into the hundred plus Hertz range), he told me something that for some reason I didn't know: harmonics of a fundamental note not only go upward but they also go downward. I don't know why I always assume they only went upward. So a human voice or an instrument is creating harmonics going all the way down and it's some of these lower harmonics that are just not reproduced well enough and fast enough by most main speakers. The subwoofers ability to reproduce those lens an air of ambience in reality that creates both conscious and subconscious improvements in the perception that you're listening to real people and real instruments in a real space.
My initial take on having a six pack is that it brings something to the system that no other upgrade can bring. It improves the general sense of reality, bringing more dimension to voices and instruments and more sense of a real room and real space. It also has a diffusing quality that some people might not like because the pinpoint imaging is not as clear, but overall I think is superior in terms of how a real room sounds with people playing instruments and singing. And one of the effects of this is that it makes digital sound much more analog. It makes almost everything I play through digital sound much less fatiguing and less flat, dimensionally.
Just thought I would share back with you guys some thoughts now that I have these up and running.
Thanks