I love my Maggies, and agree that their bass response is most often OK without subwoofer help. Just the same, I have a very elaborate built-in custom 3 channel (fronts) subwoofer system. Three 15" drivers and 3 12" drivers individually driven by six 500 watt amps.
The Maggie problem as I see it is lack of what people call "punch". Cones are good at "punch". "Punch" is what makes your stomach uneasy when the organ sounds that 32 foot pipe, and what makes your trouser legs flap when the brass band plays a Sousa march.
My subwoofer array is capable of higher frequencies than the normal subwoofer, and is, I believe, very well "integrated" with the Maggies. I say this because I can play a pink noise signal and hear no change in the overall sound as I sweep the crossover frequency from 40 Hz to around 400 Hz. However, what I am doing when I change the frequency is to transition between cone and panel drivers. I vary the crossover frequency so as to match the speaker system to the music.
I suppose that what I have is more accurately called an "alternate woofer" system, which happens to have extended LF range.